mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson
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loongarch-next
565 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Steven Rostedt (Google)
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7a1d1e4b96 |
tracing/ring-buffer: Add last_boot_info file to boot instance
If an instance is mapped to memory on boot up, create a new file called "last_boot_info" that will hold information that can be used to properly parse the raw data in the ring buffer. It will export the delta of the addresses for text and data from what it was from the last boot. It does not expose actually addresses (unless you knew what the actual address was from the last boot). The output will look like: # cat last_boot_info text delta: -268435456 data delta: -268435456 The text and data are kept separate in case they are ever made different. Link: https://lkml.kernel.org/r/20240612232026.658680738@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vineeth Pillai <vineeth@bitbyteword.org> Cc: Youssef Esmat <youssefesmat@google.com> Cc: Beau Belgrave <beaub@linux.microsoft.com> Cc: Alexander Graf <graf@amazon.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: David Howells <dhowells@redhat.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Guenter Roeck <linux@roeck-us.net> Cc: Ross Zwisler <zwisler@google.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
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Steven Rostedt (Google)
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8f3e665965 |
ring-buffer: Save text and data locations in mapped meta data
When a ring buffer is mapped to a specific address, save the address of a text function and some data. This will be used to determine the delta between the last boot and the current boot for pointers to functions as well as to data. Link: https://lkml.kernel.org/r/20240612232026.496176678@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vineeth Pillai <vineeth@bitbyteword.org> Cc: Youssef Esmat <youssefesmat@google.com> Cc: Beau Belgrave <beaub@linux.microsoft.com> Cc: Alexander Graf <graf@amazon.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: David Howells <dhowells@redhat.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Guenter Roeck <linux@roeck-us.net> Cc: Ross Zwisler <zwisler@google.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
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Steven Rostedt (Google)
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5f3b6e839f |
ring-buffer: Validate boot range memory events
Make sure all the events in each of the sub-buffers that were mapped in a memory region are valid. This moves the code that walks the buffers for time-stamp validation out of the CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS ifdef block and is used to validate the content. Only the ring buffer event meta data and time stamps are checked and not the data load. This also has a second purpose. The buffer_page structure that points to the data sub-buffers has accounting that keeps track of the number of events that are on the sub-buffer. This updates that counter as well. That counter is used in reading the buffer and knowing if the ring buffer is empty or not. Link: https://lkml.kernel.org/r/20240612232026.172503570@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vineeth Pillai <vineeth@bitbyteword.org> Cc: Youssef Esmat <youssefesmat@google.com> Cc: Beau Belgrave <beaub@linux.microsoft.com> Cc: Alexander Graf <graf@amazon.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: David Howells <dhowells@redhat.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Guenter Roeck <linux@roeck-us.net> Cc: Ross Zwisler <zwisler@google.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
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Steven Rostedt (Google)
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c76883f18e |
ring-buffer: Add test if range of boot buffer is valid
Add a test against the ring buffer memory range to see if it has valid data. The ring_buffer_meta structure is given a new field called "first_buffer" which holds the address of the first sub-buffer. This is used to both determine if the other fields are valid as well as finding the offset between the old addresses of the sub-buffer from the previous boot to the new addresses of the current boot. Since the values for nr_subbufs and subbuf_size is to be the same, check if the values in the meta page match the values calculated. Take the range of the first_buffer and the total size of all the buffers and make sure the saved head_buffer and commit_buffer fall in the range. Iterate through all the sub-buffers to make sure that the values in the sub-buffer "commit" field (the field that holds the amount of data on the sub-buffer) is within the end of the sub-buffer. Also check the index array to make sure that all the indexes are within nr_subbufs. Link: https://lkml.kernel.org/r/20240612232026.013843655@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vineeth Pillai <vineeth@bitbyteword.org> Cc: Youssef Esmat <youssefesmat@google.com> Cc: Beau Belgrave <beaub@linux.microsoft.com> Cc: Alexander Graf <graf@amazon.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: David Howells <dhowells@redhat.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Guenter Roeck <linux@roeck-us.net> Cc: Ross Zwisler <zwisler@google.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
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Steven Rostedt (Google)
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950032ffce |
ring-buffer: Add output of ring buffer meta page
Add a buffer_meta per-cpu file for the trace instance that is mapped to boot memory. This shows the current meta-data and can be used by user space tools to record off the current mappings to help reconstruct the ring buffer after a reboot. It does not expose any virtual addresses, just indexes into the sub-buffer pages. Link: https://lkml.kernel.org/r/20240612232025.854471446@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vineeth Pillai <vineeth@bitbyteword.org> Cc: Youssef Esmat <youssefesmat@google.com> Cc: Beau Belgrave <beaub@linux.microsoft.com> Cc: Alexander Graf <graf@amazon.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: David Howells <dhowells@redhat.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Guenter Roeck <linux@roeck-us.net> Cc: Ross Zwisler <zwisler@google.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
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Steven Rostedt (Google)
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b14d032973 |
ring-buffer: Add ring_buffer_meta data
Populate the ring_buffer_meta array. It holds the pointer to the head_buffer (next to read), the commit_buffer (next to write) the size of the sub-buffers, number of sub-buffers and an array that keeps track of the order of the sub-buffers. This information will be stored in the persistent memory to help on reboot to reconstruct the ring buffer. Link: https://lkml.kernel.org/r/20240612232025.530733577@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vineeth Pillai <vineeth@bitbyteword.org> Cc: Youssef Esmat <youssefesmat@google.com> Cc: Beau Belgrave <beaub@linux.microsoft.com> Cc: Alexander Graf <graf@amazon.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: David Howells <dhowells@redhat.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Guenter Roeck <linux@roeck-us.net> Cc: Ross Zwisler <zwisler@google.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
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Steven Rostedt (Google)
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be68d63a13 |
ring-buffer: Add ring_buffer_alloc_range()
In preparation to allowing the trace ring buffer to be allocated in a range of memory that is persistent across reboots, add ring_buffer_alloc_range(). It takes a contiguous range of memory and will split it up evenly for the per CPU ring buffers. If there's not enough memory to handle all CPUs with the minimum size, it will fail to allocate the ring buffer. Link: https://lkml.kernel.org/r/20240612232025.363998725@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vineeth Pillai <vineeth@bitbyteword.org> Cc: Youssef Esmat <youssefesmat@google.com> Cc: Beau Belgrave <beaub@linux.microsoft.com> Cc: Alexander Graf <graf@amazon.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: David Howells <dhowells@redhat.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Guenter Roeck <linux@roeck-us.net> Cc: Ross Zwisler <zwisler@google.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
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Steven Rostedt (Google)
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dd4900d94f |
ring-buffer: Allow mapped field to be set without mapping
In preparation for having the ring buffer mapped to a dedicated location, which will have the same restrictions as user space memory mapped buffers, allow it to use the "mapped" field of the ring_buffer_per_cpu structure without having the user space meta page mapping. When this starts using the mapped field, it will need to handle adding a user space mapping (and removing it) from a ring buffer that is using a dedicated memory range. Link: https://lkml.kernel.org/r/20240612232025.190908567@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vineeth Pillai <vineeth@bitbyteword.org> Cc: Youssef Esmat <youssefesmat@google.com> Cc: Beau Belgrave <beaub@linux.microsoft.com> Cc: Alexander Graf <graf@amazon.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: David Howells <dhowells@redhat.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Guenter Roeck <linux@roeck-us.net> Cc: Ross Zwisler <zwisler@google.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
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Petr Pavlu
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c2274b908d |
ring-buffer: Fix a race between readers and resize checks
The reader code in rb_get_reader_page() swaps a new reader page into the ring buffer by doing cmpxchg on old->list.prev->next to point it to the new page. Following that, if the operation is successful, old->list.next->prev gets updated too. This means the underlying doubly-linked list is temporarily inconsistent, page->prev->next or page->next->prev might not be equal back to page for some page in the ring buffer. The resize operation in ring_buffer_resize() can be invoked in parallel. It calls rb_check_pages() which can detect the described inconsistency and stop further tracing: [ 190.271762] ------------[ cut here ]------------ [ 190.271771] WARNING: CPU: 1 PID: 6186 at kernel/trace/ring_buffer.c:1467 rb_check_pages.isra.0+0x6a/0xa0 [ 190.271789] Modules linked in: [...] [ 190.271991] Unloaded tainted modules: intel_uncore_frequency(E):1 skx_edac(E):1 [ 190.272002] CPU: 1 PID: 6186 Comm: cmd.sh Kdump: loaded Tainted: G E 6.9.0-rc6-default #5 158d3e1e6d0b091c34c3b96bfd99a1c58306d79f [ 190.272011] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.0-0-gd239552c-rebuilt.opensuse.org 04/01/2014 [ 190.272015] RIP: 0010:rb_check_pages.isra.0+0x6a/0xa0 [ 190.272023] Code: [...] [ 190.272028] RSP: 0018:ffff9c37463abb70 EFLAGS: 00010206 [ 190.272034] RAX: ffff8eba04b6cb80 RBX: 0000000000000007 RCX: ffff8eba01f13d80 [ 190.272038] RDX: ffff8eba01f130c0 RSI: ffff8eba04b6cd00 RDI: ffff8eba0004c700 [ 190.272042] RBP: ffff8eba0004c700 R08: 0000000000010002 R09: 0000000000000000 [ 190.272045] R10: 00000000ffff7f52 R11: ffff8eba7f600000 R12: ffff8eba0004c720 [ 190.272049] R13: ffff8eba00223a00 R14: 0000000000000008 R15: ffff8eba067a8000 [ 190.272053] FS: 00007f1bd64752c0(0000) GS:ffff8eba7f680000(0000) knlGS:0000000000000000 [ 190.272057] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 190.272061] CR2: 00007f1bd6662590 CR3: 000000010291e001 CR4: 0000000000370ef0 [ 190.272070] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 190.272073] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 190.272077] Call Trace: [ 190.272098] <TASK> [ 190.272189] ring_buffer_resize+0x2ab/0x460 [ 190.272199] __tracing_resize_ring_buffer.part.0+0x23/0xa0 [ 190.272206] tracing_resize_ring_buffer+0x65/0x90 [ 190.272216] tracing_entries_write+0x74/0xc0 [ 190.272225] vfs_write+0xf5/0x420 [ 190.272248] ksys_write+0x67/0xe0 [ 190.272256] do_syscall_64+0x82/0x170 [ 190.272363] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 190.272373] RIP: 0033:0x7f1bd657d263 [ 190.272381] Code: [...] [ 190.272385] RSP: 002b:00007ffe72b643f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 [ 190.272391] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f1bd657d263 [ 190.272395] RDX: 0000000000000002 RSI: 0000555a6eb538e0 RDI: 0000000000000001 [ 190.272398] RBP: 0000555a6eb538e0 R08: 000000000000000a R09: 0000000000000000 [ 190.272401] R10: 0000555a6eb55190 R11: 0000000000000246 R12: 00007f1bd6662500 [ 190.272404] R13: 0000000000000002 R14: 00007f1bd6667c00 R15: 0000000000000002 [ 190.272412] </TASK> [ 190.272414] ---[ end trace 0000000000000000 ]--- Note that ring_buffer_resize() calls rb_check_pages() only if the parent trace_buffer has recording disabled. Recent commit |
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Petr Pavlu
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ea70a9628e |
ring-buffer: Correct stale comments related to non-consuming readers
Adjust the following code documentation: * Kernel-doc comments for ring_buffer_read_prepare() and ring_buffer_read_finish() mention that recording to the ring buffer is disabled when the read is active. Remove mention of this restriction because it was already lifted in commit |
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Steven Rostedt (Google)
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b9c6820f02 |
ring-buffer: Add cast to unsigned long addr passed to virt_to_page()
The sub-buffer pages are held in an unsigned long array, and when it is
passed to virt_to_page() a cast is needed.
Link: https://lore.kernel.org/all/20240515124808.06279d04@canb.auug.org.au/
Link: https://lore.kernel.org/linux-trace-kernel/20240515010558.4abaefdd@rorschach.local.home
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes:
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Steven Rostedt (Google)
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fe832be05a |
ring-buffer: Have mmapped ring buffer keep track of missed events
While testing libtracefs on the mmapped ring buffer, the test that checks if missed events are accounted for failed when using the mapped buffer. This is because the mapped page does not update the missed events that were dropped because the writer filled up the ring buffer before the reader could catch it. Add the missed events to the reader page/sub-buffer when the IOCTL is done and a new reader page is acquired. Note that all accesses to the reader_page via rb_page_commit() had to be switched to rb_page_size(), and rb_page_size() which was just a copy of rb_page_commit() but now it masks out the RB_MISSED bits. This is needed as the mapped reader page is still active in the ring buffer code and where it reads the commit field of the bpage for the size, it now must mask it otherwise the missed bits that are now set will corrupt the size returned. Link: https://lore.kernel.org/linux-trace-kernel/20240312175405.12fb6726@gandalf.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Vincent Donnefort <vdonnefort@google.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
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Vincent Donnefort
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117c39200d |
ring-buffer: Introducing ring-buffer mapping functions
In preparation for allowing the user-space to map a ring-buffer, add
a set of mapping functions:
ring_buffer_{map,unmap}()
And controls on the ring-buffer:
ring_buffer_map_get_reader() /* swap reader and head */
Mapping the ring-buffer also involves:
A unique ID for each subbuf of the ring-buffer, currently they are
only identified through their in-kernel VA.
A meta-page, where are stored ring-buffer statistics and a
description for the current reader
The linear mapping exposes the meta-page, and each subbuf of the
ring-buffer, ordered following their unique ID, assigned during the
first mapping.
Once mapped, no subbuf can get in or out of the ring-buffer: the buffer
size will remain unmodified and the splice enabling functions will in
reality simply memcpy the data instead of swapping subbufs.
Link: https://lore.kernel.org/linux-trace-kernel/20240510140435.3550353-3-vdonnefort@google.com
CC: <linux-mm@kvack.org>
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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Vincent Donnefort
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c09d4167b5 |
ring-buffer: Allocate sub-buffers with __GFP_COMP
In preparation for the ring-buffer memory mapping, allocate compound pages for the ring-buffer sub-buffers to enable us to map them to user-space with vm_insert_pages(). Link: https://lore.kernel.org/linux-trace-kernel/20240510140435.3550353-2-vdonnefort@google.com Acked-by: David Hildenbrand <david@redhat.com> Signed-off-by: Vincent Donnefort <vdonnefort@google.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
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Steven Rostedt (Google)
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ffe3986fec |
ring-buffer: Only update pages_touched when a new page is touched
The "buffer_percent" logic that is used by the ring buffer splice code to
only wake up the tasks when there's no data after the buffer is filled to
the percentage of the "buffer_percent" file is dependent on three
variables that determine the amount of data that is in the ring buffer:
1) pages_read - incremented whenever a new sub-buffer is consumed
2) pages_lost - incremented every time a writer overwrites a sub-buffer
3) pages_touched - incremented when a write goes to a new sub-buffer
The percentage is the calculation of:
(pages_touched - (pages_lost + pages_read)) / nr_pages
Basically, the amount of data is the total number of sub-bufs that have been
touched, minus the number of sub-bufs lost and sub-bufs consumed. This is
divided by the total count to give the buffer percentage. When the
percentage is greater than the value in the "buffer_percent" file, it
wakes up splice readers waiting for that amount.
It was observed that over time, the amount read from the splice was
constantly decreasing the longer the trace was running. That is, if one
asked for 60%, it would read over 60% when it first starts tracing, but
then it would be woken up at under 60% and would slowly decrease the
amount of data read after being woken up, where the amount becomes much
less than the buffer percent.
This was due to an accounting of the pages_touched incrementation. This
value is incremented whenever a writer transfers to a new sub-buffer. But
the place where it was incremented was incorrect. If a writer overflowed
the current sub-buffer it would go to the next one. If it gets preempted
by an interrupt at that time, and the interrupt performs a trace, it too
will end up going to the next sub-buffer. But only one should increment
the counter. Unfortunately, that was not the case.
Change the cmpxchg() that does the real switch of the tail-page into a
try_cmpxchg(), and on success, perform the increment of pages_touched. This
will only increment the counter once for when the writer moves to a new
sub-buffer, and not when there's a race and is incremented for when a
writer and its preempting writer both move to the same new sub-buffer.
Link: https://lore.kernel.org/linux-trace-kernel/20240409151309.0d0e5056@gandalf.local.home
Cc: stable@vger.kernel.org
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes:
|
||
|
Steven Rostedt (Google)
|
b70f293824 |
ring-buffer: Make wake once of ring_buffer_wait() more robust
The default behavior of ring_buffer_wait() when passed a NULL "cond"
parameter is to exit the function the first time it is woken up. The
current implementation uses a counter that starts at zero and when it is
greater than one it exits the wait_event_interruptible().
But this relies on the internal working of wait_event_interruptible() as
that code basically has:
if (cond)
return;
prepare_to_wait();
if (!cond)
schedule();
finish_wait();
That is, cond is called twice before it sleeps. The default cond of
ring_buffer_wait() needs to account for that and wait for its counter to
increment twice before exiting.
Instead, use the seq/atomic_inc logic that is used by the tracing code
that calls this function. Add an atomic_t seq to rb_irq_work and when cond
is NULL, have the default callback take a descriptor as its data that
holds the rbwork and the value of the seq when it started.
The wakeups will now increment the rbwork->seq and the cond callback will
simply check if that number is different, and no longer have to rely on
the implementation of wait_event_interruptible().
Link: https://lore.kernel.org/linux-trace-kernel/20240315063115.6cb5d205@gandalf.local.home
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes:
|
||
|
linke li
|
f1e30cb636 |
ring-buffer: use READ_ONCE() to read cpu_buffer->commit_page in concurrent environment
In function ring_buffer_iter_empty(), cpu_buffer->commit_page is read while other threads may change it. It may cause the time_stamp that read in the next line come from a different page. Use READ_ONCE() to avoid having to reason about compiler optimizations now and in future. Link: https://lore.kernel.org/linux-trace-kernel/tencent_DFF7D3561A0686B5E8FC079150A02505180A@qq.com Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: linke li <lilinke99@qq.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Vincent Donnefort
|
6b76323e5a |
ring-buffer: Zero ring-buffer sub-buffers
In preparation for the ring-buffer memory mapping where each subbuf will be accessible to user-space, zero all the page allocations. Link: https://lore.kernel.org/linux-trace-kernel/20240220202310.2489614-2-vdonnefort@google.com Signed-off-by: Vincent Donnefort <vdonnefort@google.com> Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Linus Torvalds
|
63bd30f249 |
Tracing/ring-buffer fixes for 6.8 (to be applied in 6.9-rc):
- Do not update shortest_full in rb_watermark_hit() if the watermark is hit. The shortest_full field was being updated regardless if the task was going to wait or not. If the watermark is hit, then the task is not going to wait, so do not update the shortest_full field (used by the waker). - Update shortest_full field before setting the full_waiters_pending flag In the poll logic, the full_waiters_pending flag was being set before the shortest_full field was set. If the full_waiters_pending flag is set, writers will check the shortest_full field which has the least percentage of data that the ring buffer needs to be filled before waking up. The writer will check shortest_full if full_waiters_pending is set, and if the ring buffer percentage filled is greater than shortest full, then it will call the irq_work to wake up the waiters. The problem was that the poll logic set the full_waiters_pending flag before updating shortest_full, which when zero will always trigger the writer to call the irq_work to wake up the waiters. The irq_work will reset the shortest_full field back to zero as the woken waiters is suppose to reset it. - There's some optimized logic in the rb_watermark_hit() that is used in ring_buffer_wait(). Use that helper function in the poll logic as well. - Restructure ring_buffer_wait() to use wait_event_interruptible() The logic to wake up pending readers when the file descriptor is closed is racy. Restructure ring_buffer_wait() to allow callers to pass in conditions besides the ring buffer having enough data in it by using wait_event_interruptible(). - Update the tracing_wait_on_pipe() to call ring_buffer_wait() with its own conditions to exit the wait loop. -----BEGIN PGP SIGNATURE----- iIoEABYIADIWIQRRSw7ePDh/lE+zeZMp5XQQmuv6qgUCZfH6MRQccm9zdGVkdEBn b29kbWlzLm9yZwAKCRAp5XQQmuv6qtlwAP9ZoSIkvw2MVu7FclgAguaX2CaylGEw sv0wZaCy1kgAPgD8CFhezZcHrt/RwJibpMxVnUs+DDqYnGdJsHYLihlbWgg= =99FG -----END PGP SIGNATURE----- Merge tag 'trace-ring-buffer-v6.8-rc7-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing updates from Steven Rostedt: - Do not update shortest_full in rb_watermark_hit() if the watermark is hit. The shortest_full field was being updated regardless if the task was going to wait or not. If the watermark is hit, then the task is not going to wait, so do not update the shortest_full field (used by the waker). - Update shortest_full field before setting the full_waiters_pending flag In the poll logic, the full_waiters_pending flag was being set before the shortest_full field was set. If the full_waiters_pending flag is set, writers will check the shortest_full field which has the least percentage of data that the ring buffer needs to be filled before waking up. The writer will check shortest_full if full_waiters_pending is set, and if the ring buffer percentage filled is greater than shortest full, then it will call the irq_work to wake up the waiters. The problem was that the poll logic set the full_waiters_pending flag before updating shortest_full, which when zero will always trigger the writer to call the irq_work to wake up the waiters. The irq_work will reset the shortest_full field back to zero as the woken waiters is suppose to reset it. - There's some optimized logic in the rb_watermark_hit() that is used in ring_buffer_wait(). Use that helper function in the poll logic as well. - Restructure ring_buffer_wait() to use wait_event_interruptible() The logic to wake up pending readers when the file descriptor is closed is racy. Restructure ring_buffer_wait() to allow callers to pass in conditions besides the ring buffer having enough data in it by using wait_event_interruptible(). - Update the tracing_wait_on_pipe() to call ring_buffer_wait() with its own conditions to exit the wait loop. * tag 'trace-ring-buffer-v6.8-rc7-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: tracing/ring-buffer: Fix wait_on_pipe() race ring-buffer: Use wait_event_interruptible() in ring_buffer_wait() ring-buffer: Reuse rb_watermark_hit() for the poll logic ring-buffer: Fix full_waiters_pending in poll ring-buffer: Do not set shortest_full when full target is hit |
||
|
Steven Rostedt (Google)
|
2aa043a55b |
tracing/ring-buffer: Fix wait_on_pipe() race
When the trace_pipe_raw file is closed, there should be no new readers on
the file descriptor. This is mostly handled with the waking and wait_index
fields of the iterator. But there's still a slight race.
CPU 0 CPU 1
----- -----
wait_index++;
index = wait_index;
ring_buffer_wake_waiters();
wait_on_pipe()
ring_buffer_wait();
The ring_buffer_wait() will miss the wakeup from CPU 1. The problem is
that the ring_buffer_wait() needs the logic of:
prepare_to_wait();
if (!condition)
schedule();
Where the missing condition check is the iter->wait_index update.
Have the ring_buffer_wait() take a conditional callback function and a
data parameter that can be used within the wait_event_interruptible() of
the ring_buffer_wait() function.
In wait_on_pipe(), pass a condition function that will check if the
wait_index has been updated, if it has, it will return true to break out
of the wait_event_interruptible() loop.
Create a new field "closed" in the trace_iterator and set it in the
.flush() callback before calling ring_buffer_wake_waiters().
This will keep any new readers from waiting on a closed file descriptor.
Have the wait_on_pipe() condition callback also check the closed field.
Change the wait_index field of the trace_iterator to atomic_t. There's no
reason it needs to be 'long' and making it atomic and using
atomic_read_acquire() and atomic_fetch_inc_release() will provide the
necessary memory barriers.
Add a "woken" flag to tracing_buffers_splice_read() to exit the loop after
one more try to fetch data. That is, if it waited for data and something
woke it up, it should try to collect any new data and then exit back to
user space.
Link: https://lore.kernel.org/linux-trace-kernel/CAHk-=wgsNgewHFxZAJiAQznwPMqEtQmi1waeS2O1v6L4c_Um5A@mail.gmail.com/
Link: https://lore.kernel.org/linux-trace-kernel/20240312121703.557950713@goodmis.org
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linke li <lilinke99@qq.com>
Cc: Rabin Vincent <rabin@rab.in>
Fixes:
|
||
|
Steven Rostedt (Google)
|
7af9ded0c2 |
ring-buffer: Use wait_event_interruptible() in ring_buffer_wait()
Convert ring_buffer_wait() over to wait_event_interruptible(). The default
condition is to execute the wait loop inside __wait_event() just once.
This does not change the ring_buffer_wait() prototype yet, but
restructures the code so that it can take a "cond" and "data" parameter
and will call wait_event_interruptible() with a helper function as the
condition.
The helper function (rb_wait_cond) takes the cond function and data
parameters. It will first check if the buffer hit the watermark defined by
the "full" parameter and then call the passed in condition parameter. If
either are true, it returns true.
If rb_wait_cond() does not return true, it will set the appropriate
"waiters_pending" flag and returns false.
Link: https://lore.kernel.org/linux-trace-kernel/CAHk-=wgsNgewHFxZAJiAQznwPMqEtQmi1waeS2O1v6L4c_Um5A@mail.gmail.com/
Link: https://lore.kernel.org/linux-trace-kernel/20240312121703.399598519@goodmis.org
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linke li <lilinke99@qq.com>
Cc: Rabin Vincent <rabin@rab.in>
Fixes:
|
||
|
Steven Rostedt (Google)
|
e36f19a645 |
ring-buffer: Reuse rb_watermark_hit() for the poll logic
The check for knowing if the poll should wait or not is basically the exact same logic as rb_watermark_hit(). The only difference is that rb_watermark_hit() also handles the !full case. But for the full case, the logic is the same. Just call that instead of duplicating the code in ring_buffer_poll_wait(). Link: https://lore.kernel.org/linux-trace-kernel/20240312131952.802267543@goodmis.org Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Steven Rostedt (Google)
|
8145f1c35f |
ring-buffer: Fix full_waiters_pending in poll
If a reader of the ring buffer is doing a poll, and waiting for the ring
buffer to hit a specific watermark, there could be a case where it gets
into an infinite ping-pong loop.
The poll code has:
rbwork->full_waiters_pending = true;
if (!cpu_buffer->shortest_full ||
cpu_buffer->shortest_full > full)
cpu_buffer->shortest_full = full;
The writer will see full_waiters_pending and check if the ring buffer is
filled over the percentage of the shortest_full value. If it is, it calls
an irq_work to wake up all the waiters.
But the code could get into a circular loop:
CPU 0 CPU 1
----- -----
[ Poll ]
[ shortest_full = 0 ]
rbwork->full_waiters_pending = true;
if (rbwork->full_waiters_pending &&
[ buffer percent ] > shortest_full) {
rbwork->wakeup_full = true;
[ queue_irqwork ]
cpu_buffer->shortest_full = full;
[ IRQ work ]
if (rbwork->wakeup_full) {
cpu_buffer->shortest_full = 0;
wakeup poll waiters;
[woken]
if ([ buffer percent ] > full)
break;
rbwork->full_waiters_pending = true;
if (rbwork->full_waiters_pending &&
[ buffer percent ] > shortest_full) {
rbwork->wakeup_full = true;
[ queue_irqwork ]
cpu_buffer->shortest_full = full;
[ IRQ work ]
if (rbwork->wakeup_full) {
cpu_buffer->shortest_full = 0;
wakeup poll waiters;
[woken]
[ Wash, rinse, repeat! ]
In the poll, the shortest_full needs to be set before the
full_pending_waiters, as once that is set, the writer will compare the
current shortest_full (which is incorrect) to decide to call the irq_work,
which will reset the shortest_full (expecting the readers to update it).
Also move the setting of full_waiters_pending after the check if the ring
buffer has the required percentage filled. There's no reason to tell the
writer to wake up waiters if there are no waiters.
Link: https://lore.kernel.org/linux-trace-kernel/20240312131952.630922155@goodmis.org
Cc: stable@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes:
|
||
|
Steven Rostedt (Google)
|
761d9473e2 |
ring-buffer: Do not set shortest_full when full target is hit
The rb_watermark_hit() checks if the amount of data in the ring buffer is
above the percentage level passed in by the "full" variable. If it is, it
returns true.
But it also sets the "shortest_full" field of the cpu_buffer that informs
writers that it needs to call the irq_work if the amount of data on the
ring buffer is above the requested amount.
The rb_watermark_hit() always sets the shortest_full even if the amount in
the ring buffer is what it wants. As it is not going to wait, because it
has what it wants, there's no reason to set shortest_full.
Link: https://lore.kernel.org/linux-trace-kernel/20240312115641.6aa8ba08@gandalf.local.home
Cc: stable@vger.kernel.org
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes:
|
||
|
Linus Torvalds
|
685d982112 |
Core x86 changes for v6.9:
- The biggest change is the rework of the percpu code,
to support the 'Named Address Spaces' GCC feature,
by Uros Bizjak:
- This allows C code to access GS and FS segment relative
memory via variables declared with such attributes,
which allows the compiler to better optimize those accesses
than the previous inline assembly code.
- The series also includes a number of micro-optimizations
for various percpu access methods, plus a number of
cleanups of %gs accesses in assembly code.
- These changes have been exposed to linux-next testing for
the last ~5 months, with no known regressions in this area.
- Fix/clean up __switch_to()'s broken but accidentally
working handling of FPU switching - which also generates
better code.
- Propagate more RIP-relative addressing in assembly code,
to generate slightly better code.
- Rework the CPU mitigations Kconfig space to be less idiosyncratic,
to make it easier for distros to follow & maintain these options.
- Rework the x86 idle code to cure RCU violations and
to clean up the logic.
- Clean up the vDSO Makefile logic.
- Misc cleanups and fixes.
[ Please note that there's a higher number of merge commits in
this branch (three) than is usual in x86 topic trees. This happened
due to the long testing lifecycle of the percpu changes that
involved 3 merge windows, which generated a longer history
and various interactions with other core x86 changes that we
felt better about to carry in a single branch. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'x86-core-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull core x86 updates from Ingo Molnar:
- The biggest change is the rework of the percpu code, to support the
'Named Address Spaces' GCC feature, by Uros Bizjak:
- This allows C code to access GS and FS segment relative memory
via variables declared with such attributes, which allows the
compiler to better optimize those accesses than the previous
inline assembly code.
- The series also includes a number of micro-optimizations for
various percpu access methods, plus a number of cleanups of %gs
accesses in assembly code.
- These changes have been exposed to linux-next testing for the
last ~5 months, with no known regressions in this area.
- Fix/clean up __switch_to()'s broken but accidentally working handling
of FPU switching - which also generates better code
- Propagate more RIP-relative addressing in assembly code, to generate
slightly better code
- Rework the CPU mitigations Kconfig space to be less idiosyncratic, to
make it easier for distros to follow & maintain these options
- Rework the x86 idle code to cure RCU violations and to clean up the
logic
- Clean up the vDSO Makefile logic
- Misc cleanups and fixes
* tag 'x86-core-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (52 commits)
x86/idle: Select idle routine only once
x86/idle: Let prefer_mwait_c1_over_halt() return bool
x86/idle: Cleanup idle_setup()
x86/idle: Clean up idle selection
x86/idle: Sanitize X86_BUG_AMD_E400 handling
sched/idle: Conditionally handle tick broadcast in default_idle_call()
x86: Increase brk randomness entropy for 64-bit systems
x86/vdso: Move vDSO to mmap region
x86/vdso/kbuild: Group non-standard build attributes and primary object file rules together
x86/vdso: Fix rethunk patching for vdso-image-{32,64}.o
x86/retpoline: Ensure default return thunk isn't used at runtime
x86/vdso: Use CONFIG_COMPAT_32 to specify vdso32
x86/vdso: Use $(addprefix ) instead of $(foreach )
x86/vdso: Simplify obj-y addition
x86/vdso: Consolidate targets and clean-files
x86/bugs: Rename CONFIG_RETHUNK => CONFIG_MITIGATION_RETHUNK
x86/bugs: Rename CONFIG_CPU_SRSO => CONFIG_MITIGATION_SRSO
x86/bugs: Rename CONFIG_CPU_IBRS_ENTRY => CONFIG_MITIGATION_IBRS_ENTRY
x86/bugs: Rename CONFIG_CPU_UNRET_ENTRY => CONFIG_MITIGATION_UNRET_ENTRY
x86/bugs: Rename CONFIG_SLS => CONFIG_MITIGATION_SLS
...
|
||
|
Steven Rostedt (Google)
|
68282dd930 |
ring-buffer: Fix resetting of shortest_full
The "shortest_full" variable is used to keep track of the waiter that is
waiting for the smallest amount on the ring buffer before being woken up.
When a tasks waits on the ring buffer, it passes in a "full" value that is
a percentage. 0 means wake up on any data. 1-100 means wake up from 1% to
100% full buffer.
As all waiters are on the same wait queue, the wake up happens for the
waiter with the smallest percentage.
The problem is that the smallest_full on the cpu_buffer that stores the
smallest amount doesn't get reset when all the waiters are woken up. It
does get reset when the ring buffer is reset (echo > /sys/kernel/tracing/trace).
This means that tasks may be woken up more often then when they want to
be. Instead, have the shortest_full field get reset just before waking up
all the tasks. If the tasks wait again, they will update the shortest_full
before sleeping.
Also add locking around setting of shortest_full in the poll logic, and
change "work" to "rbwork" to match the variable name for rb_irq_work
structures that are used in other places.
Link: https://lore.kernel.org/linux-trace-kernel/20240308202431.948914369@goodmis.org
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linke li <lilinke99@qq.com>
Cc: Rabin Vincent <rabin@rab.in>
Fixes:
|
||
|
Steven Rostedt (Google)
|
b359457368 |
ring-buffer: Fix waking up ring buffer readers
A task can wait on a ring buffer for when it fills up to a specific
watermark. The writer will check the minimum watermark that waiters are
waiting for and if the ring buffer is past that, it will wake up all the
waiters.
The waiters are in a wait loop, and will first check if a signal is
pending and then check if the ring buffer is at the desired level where it
should break out of the loop.
If a file that uses a ring buffer closes, and there's threads waiting on
the ring buffer, it needs to wake up those threads. To do this, a
"wait_index" was used.
Before entering the wait loop, the waiter will read the wait_index. On
wakeup, it will check if the wait_index is different than when it entered
the loop, and will exit the loop if it is. The waker will only need to
update the wait_index before waking up the waiters.
This had a couple of bugs. One trivial one and one broken by design.
The trivial bug was that the waiter checked the wait_index after the
schedule() call. It had to be checked between the prepare_to_wait() and
the schedule() which it was not.
The main bug is that the first check to set the default wait_index will
always be outside the prepare_to_wait() and the schedule(). That's because
the ring_buffer_wait() doesn't have enough context to know if it should
break out of the loop.
The loop itself is not needed, because all the callers to the
ring_buffer_wait() also has their own loop, as the callers have a better
sense of what the context is to decide whether to break out of the loop
or not.
Just have the ring_buffer_wait() block once, and if it gets woken up, exit
the function and let the callers decide what to do next.
Link: https://lore.kernel.org/all/CAHk-=whs5MdtNjzFkTyaUy=vHi=qwWgPi0JgTe6OYUYMNSRZfg@mail.gmail.com/
Link: https://lore.kernel.org/linux-trace-kernel/20240308202431.792933613@goodmis.org
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linke li <lilinke99@qq.com>
Cc: Rabin Vincent <rabin@rab.in>
Fixes:
|
||
|
Steven Rostedt (Google)
|
e78fb4eac8 |
ring-buffer: Do not let subbuf be bigger than write mask
The data on the subbuffer is measured by a write variable that also
contains status flags. The counter is just 20 bits in length. If the
subbuffer is bigger than then counter, it will fail.
Make sure that the subbuffer can not be set to greater than the counter
that keeps track of the data on the subbuffer.
Link: https://lore.kernel.org/linux-trace-kernel/20240220095112.77e9cb81@gandalf.local.home
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes:
|
||
|
Ingo Molnar
|
4589f199eb |
Merge branch 'x86/bugs' into x86/core, to pick up pending changes before dependent patches
Merge in pending alternatives patching infrastructure changes, before applying more patches. Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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Vincent Donnefort
|
66bbea9ed6 |
ring-buffer: Clean ring_buffer_poll_wait() error return
The return type for ring_buffer_poll_wait() is __poll_t. This is behind
the scenes an unsigned where we can set event bits. In case of a
non-allocated CPU, we do return instead -EINVAL (0xffffffea). Lucky us,
this ends up setting few error bits (EPOLLERR | EPOLLHUP | EPOLLNVAL), so
user-space at least is aware something went wrong.
Nonetheless, this is an incorrect code. Replace that -EINVAL with a
proper EPOLLERR to clean that output. As this doesn't change the
behaviour, there's no need to treat this change as a bug fix.
Link: https://lore.kernel.org/linux-trace-kernel/20240131140955.3322792-1-vdonnefort@google.com
Cc: stable@vger.kernel.org
Fixes:
|
||
|
Linus Torvalds
|
a2ded784cd |
tracing updates for 6.8:
- Allow kernel trace instance creation to specify what events are created Inside the kernel, a subsystem may create a tracing instance that it can use to send events to user space. This sub-system may not care about the thousands of events that exist in eventfs. Allow the sub-system to specify what sub-systems of events it cares about, and only those events are exposed to this instance. - Allow the ring buffer to be broken up into bigger sub-buffers than just the architecture page size. A new tracefs file called "buffer_subbuf_size_kb" is created. The user can now specify a minimum size the sub-buffer may be in kilobytes. Note, that the implementation currently make the sub-buffer size a power of 2 pages (1, 2, 4, 8, 16, ...) but the user only writes in kilobyte size, and the sub-buffer will be updated to the next size that it will can accommodate it. If the user writes in 10, it will change the size to be 4 pages on x86 (16K), as that is the next available size that can hold 10K pages. - Update the debug output when a corrupt time is detected in the ring buffer. If the ring buffer detects inconsistent timestamps, there's a debug config options that will dump the contents of the meta data of the sub-buffer that is used for debugging. Add some more information to this dump that helps with debugging. - Add more timestamp debugging checks (only triggers when the config is enabled) - Increase the trace_seq iterator to 2 page sizes. - Allow strings written into tracefs_marker to be larger. Up to just under 2 page sizes (based on what trace_seq can hold). - Increase the trace_maker_raw write to be as big as a sub-buffer can hold. - Remove 32 bit time stamp logic, now that the rb_time_cmpxchg() has been removed. - More selftests were added. - Some code clean ups as well. -----BEGIN PGP SIGNATURE----- iIoEABYIADIWIQRRSw7ePDh/lE+zeZMp5XQQmuv6qgUCZZ8p3BQccm9zdGVkdEBn b29kbWlzLm9yZwAKCRAp5XQQmuv6ql2GAQDZg/zlFEiJHyTfWbCIE8pA3T5xbzKo 26TNxIZAxJJZpQEAvGFU5Smy14pG6soEoVMp8B6ZOANbqU8VVamhOL+r+Qw= =0OYG -----END PGP SIGNATURE----- Merge tag 'trace-v6.8' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing updates from Steven Rostedt: - Allow kernel trace instance creation to specify what events are created Inside the kernel, a subsystem may create a tracing instance that it can use to send events to user space. This sub-system may not care about the thousands of events that exist in eventfs. Allow the sub-system to specify what sub-systems of events it cares about, and only those events are exposed to this instance. - Allow the ring buffer to be broken up into bigger sub-buffers than just the architecture page size. A new tracefs file called "buffer_subbuf_size_kb" is created. The user can now specify a minimum size the sub-buffer may be in kilobytes. Note, that the implementation currently make the sub-buffer size a power of 2 pages (1, 2, 4, 8, 16, ...) but the user only writes in kilobyte size, and the sub-buffer will be updated to the next size that it will can accommodate it. If the user writes in 10, it will change the size to be 4 pages on x86 (16K), as that is the next available size that can hold 10K pages. - Update the debug output when a corrupt time is detected in the ring buffer. If the ring buffer detects inconsistent timestamps, there's a debug config options that will dump the contents of the meta data of the sub-buffer that is used for debugging. Add some more information to this dump that helps with debugging. - Add more timestamp debugging checks (only triggers when the config is enabled) - Increase the trace_seq iterator to 2 page sizes. - Allow strings written into tracefs_marker to be larger. Up to just under 2 page sizes (based on what trace_seq can hold). - Increase the trace_maker_raw write to be as big as a sub-buffer can hold. - Remove 32 bit time stamp logic, now that the rb_time_cmpxchg() has been removed. - More selftests were added. - Some code clean ups as well. * tag 'trace-v6.8' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (29 commits) ring-buffer: Remove stale comment from ring_buffer_size() tracing histograms: Simplify parse_actions() function tracing/selftests: Remove exec permissions from trace_marker.tc test ring-buffer: Use subbuf_order for buffer page masking tracing: Update subbuffer with kilobytes not page order ringbuffer/selftest: Add basic selftest to test changing subbuf order ring-buffer: Add documentation on the buffer_subbuf_order file ring-buffer: Just update the subbuffers when changing their allocation order ring-buffer: Keep the same size when updating the order tracing: Stop the tracing while changing the ring buffer subbuf size tracing: Update snapshot order along with main buffer order ring-buffer: Make sure the spare sub buffer used for reads has same size ring-buffer: Do no swap cpu buffers if order is different ring-buffer: Clear pages on error in ring_buffer_subbuf_order_set() failure ring-buffer: Read and write to ring buffers with custom sub buffer size ring-buffer: Set new size of the ring buffer sub page ring-buffer: Add interface for configuring trace sub buffer size ring-buffer: Page size per ring buffer ring-buffer: Have ring_buffer_print_page_header() be able to access ring_buffer_iter ring-buffer: Check if absolute timestamp goes backwards ... |
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|
Breno Leitao
|
aefb2f2e61 |
x86/bugs: Rename CONFIG_RETPOLINE => CONFIG_MITIGATION_RETPOLINE
Step 5/10 of the namespace unification of CPU mitigations related Kconfig options. [ mingo: Converted a few more uses in comments/messages as well. ] Suggested-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Breno Leitao <leitao@debian.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Ariel Miculas <amiculas@cisco.com> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/20231121160740.1249350-6-leitao@debian.org |
||
|
Steven Rostedt (Google)
|
25742aeb13 |
ring-buffer: Remove stale comment from ring_buffer_size()
It's been 11 years since the ring_buffer_size() function was updated to use the nr_pages from the buffer->buffers[cpu] structure instead of using the buffer->nr_pages that no longer exists. The comment in the code is more of what a change log should have and is pretty much useless for development. It's saying how things worked back in 2012 that bares no purpose on today's code. Remove it. Link: https://lore.kernel.org/linux-trace-kernel/84d3b41a72bd43dbb9d44921ef535c92@AcuMS.aculab.com/ Link: https://lore.kernel.org/linux-trace-kernel/20231220081028.7cd7e8e2@gandalf.local.home Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Reported-by: David Laight <David.Laight@ACULAB.COM> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> |
||
|
Steven Rostedt (Google)
|
39a7dc23a1 |
tracing: Fix blocked reader of snapshot buffer
If an application blocks on the snapshot or snapshot_raw files, expecting
to be woken up when a snapshot occurs, it will not happen. Or it may
happen with an unexpected result.
That result is that the application will be reading the main buffer
instead of the snapshot buffer. That is because when the snapshot occurs,
the main and snapshot buffers are swapped. But the reader has a descriptor
still pointing to the buffer that it originally connected to.
This is fine for the main buffer readers, as they may be blocked waiting
for a watermark to be hit, and when a snapshot occurs, the data that the
main readers want is now on the snapshot buffer.
But for waiters of the snapshot buffer, they are waiting for an event to
occur that will trigger the snapshot and they can then consume it quickly
to save the snapshot before the next snapshot occurs. But to do this, they
need to read the new snapshot buffer, not the old one that is now
receiving new data.
Also, it does not make sense to have a watermark "buffer_percent" on the
snapshot buffer, as the snapshot buffer is static and does not receive new
data except all at once.
Link: https://lore.kernel.org/linux-trace-kernel/20231228095149.77f5b45d@gandalf.local.home
Cc: stable@vger.kernel.org
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Fixes:
|
||
|
Steven Rostedt (Google)
|
623b1f896f |
ring-buffer: Fix wake ups when buffer_percent is set to 100
The tracefs file "buffer_percent" is to allow user space to set a
water-mark on how much of the tracing ring buffer needs to be filled in
order to wake up a blocked reader.
0 - is to wait until any data is in the buffer
1 - is to wait for 1% of the sub buffers to be filled
50 - would be half of the sub buffers are filled with data
100 - is not to wake the waiter until the ring buffer is completely full
Unfortunately the test for being full was:
dirty = ring_buffer_nr_dirty_pages(buffer, cpu);
return (dirty * 100) > (full * nr_pages);
Where "full" is the value for "buffer_percent".
There is two issues with the above when full == 100.
1. dirty * 100 > 100 * nr_pages will never be true
That is, the above is basically saying that if the user sets
buffer_percent to 100, more pages need to be dirty than exist in the
ring buffer!
2. The page that the writer is on is never considered dirty, as dirty
pages are only those that are full. When the writer goes to a new
sub-buffer, it clears the contents of that sub-buffer.
That is, even if the check was ">=" it would still not be equal as the
most pages that can be considered "dirty" is nr_pages - 1.
To fix this, add one to dirty and use ">=" in the compare.
Link: https://lore.kernel.org/linux-trace-kernel/20231226125902.4a057f1d@gandalf.local.home
Cc: stable@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Fixes:
|
||
|
Steven Rostedt (Google)
|
3cb3091138 |
ring-buffer: Use subbuf_order for buffer page masking
The comparisons to PAGE_SIZE were all converted to use the
buffer->subbuf_order, but the use of PAGE_MASK was missed.
Convert all the PAGE_MASK usages over to:
(PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1
Link: https://lore.kernel.org/linux-trace-kernel/20231219173800.66eefb7a@gandalf.local.home
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Fixes:
|
||
|
Steven Rostedt (Google)
|
8e7b58c27b |
ring-buffer: Just update the subbuffers when changing their allocation order
The ring_buffer_subbuf_order_set() was creating ring_buffer_per_cpu
cpu_buffers with the new subbuffers with the updated order, and if they
all successfully were created, then they the ring_buffer's per_cpu buffers
would be freed and replaced by them.
The problem is that the freed per_cpu buffers contains state that would be
lost. Running the following commands:
1. # echo 3 > /sys/kernel/tracing/buffer_subbuf_order
2. # echo 0 > /sys/kernel/tracing/tracing_cpumask
3. # echo 1 > /sys/kernel/tracing/snapshot
4. # echo ff > /sys/kernel/tracing/tracing_cpumask
5. # echo test > /sys/kernel/tracing/trace_marker
Would result in:
-bash: echo: write error: Bad file descriptor
That's because the state of the per_cpu buffers of the snapshot buffer is
lost when the order is changed (the order of a freed snapshot buffer goes
to 0 to save memory, and when the snapshot buffer is allocated again, it
goes back to what the main buffer is).
In operation 2, the snapshot buffers were set to "disable" (as all the
ring buffers CPUs were disabled).
In operation 3, the snapshot is allocated and a call to
ring_buffer_subbuf_order_set() replaced the per_cpu buffers losing the
"record_disable" count.
When it was enabled again, the atomic_dec(&cpu_buffer->record_disable) was
decrementing a zero, setting it to -1. Writing 1 into the snapshot would
swap the snapshot buffer with the main buffer, so now the main buffer is
"disabled", and nothing can write to the ring buffer anymore.
Instead of creating new per_cpu buffers and losing the state of the old
buffers, basically do what the resize does and just allocate new subbuf
pages into the new_pages link list of the per_cpu buffer and if they all
succeed, then replace the old sub buffers with the new ones. This keeps
the per_cpu buffer descriptor in tact and by doing so, keeps its state.
Link: https://lore.kernel.org/linux-trace-kernel/20231219185630.944104939@goodmis.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Fixes:
|
||
|
Steven Rostedt (Google)
|
353cc21937 |
ring-buffer: Keep the same size when updating the order
The function ring_buffer_subbuf_order_set() just updated the sub-buffers
to the new size, but this also changes the size of the buffer in doing so.
As the size is determined by nr_pages * subbuf_size. If the subbuf_size is
increased without decreasing the nr_pages, this causes the total size of
the buffer to increase.
This broke the latency tracers as the snapshot needs to be the same size
as the main buffer. The size of the snapshot buffer is only expanded when
needed, and because the order is still the same, the size becomes out of
sync with the main buffer, as the main buffer increased in size without
the tracing system knowing.
Calculate the nr_pages to allocate with the new subbuf_size to be
buffer_size / new_subbuf_size.
Link: https://lore.kernel.org/linux-trace-kernel/20231219185630.649397785@goodmis.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Fixes:
|
||
|
Steven Rostedt (Google)
|
b81e03a249 |
ring-buffer: Do no swap cpu buffers if order is different
As all the subbuffer order (subbuffer sizes) must be the same throughout the ring buffer, check the order of the buffers that are doing a CPU buffer swap in ring_buffer_swap_cpu() to make sure they are the same. If the are not the same, then fail to do the swap, otherwise the ring buffer will think the CPU buffer has a specific subbuffer size when it does not. Link: https://lore.kernel.org/linux-trace-kernel/20231219185629.467894710@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Tzvetomir Stoyanov <tz.stoyanov@gmail.com> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Kent Overstreet <kent.overstreet@gmail.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Steven Rostedt (Google)
|
22887dfba0 |
ring-buffer: Clear pages on error in ring_buffer_subbuf_order_set() failure
On failure to allocate ring buffer pages, the pointer to the CPU buffer
pages is freed, but the pages that were allocated previously were not.
Make sure they are freed too.
Link: https://lore.kernel.org/linux-trace-kernel/20231219185629.179352802@goodmis.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Fixes:
|
||
|
Tzvetomir Stoyanov (VMware)
|
bce761d757 |
ring-buffer: Read and write to ring buffers with custom sub buffer size
As the size of the ring sub buffer page can be changed dynamically, the logic that reads and writes to the buffer should be fixed to take that into account. Some internal ring buffer APIs are changed: ring_buffer_alloc_read_page() ring_buffer_free_read_page() ring_buffer_read_page() A new API is introduced: ring_buffer_read_page_data() Link: https://lore.kernel.org/linux-trace-devel/20211213094825.61876-6-tz.stoyanov@gmail.com Link: https://lore.kernel.org/linux-trace-kernel/20231219185628.875145995@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Kent Overstreet <kent.overstreet@gmail.com> Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com> [ Fixed kerneldoc on data_page parameter in ring_buffer_free_read_page() ] Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Tzvetomir Stoyanov (VMware)
|
f9b94daa54 |
ring-buffer: Set new size of the ring buffer sub page
There are two approaches when changing the size of the ring buffer
sub page:
1. Destroying all pages and allocating new pages with the new size.
2. Allocating new pages, copying the content of the old pages before
destroying them.
The first approach is easier, it is selected in the proposed
implementation. Changing the ring buffer sub page size is supposed to
not happen frequently. Usually, that size should be set only once,
when the buffer is not in use yet and is supposed to be empty.
Link: https://lore.kernel.org/linux-trace-devel/20211213094825.61876-5-tz.stoyanov@gmail.com
Link: https://lore.kernel.org/linux-trace-kernel/20231219185628.588995543@goodmis.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
|
||
|
Tzvetomir Stoyanov (VMware)
|
2808e31ec1 |
ring-buffer: Add interface for configuring trace sub buffer size
The trace ring buffer sub page size can be configured, per trace instance. A new ftrace file "buffer_subbuf_order" is added to get and set the size of the ring buffer sub page for current trace instance. The size must be an order of system page size, that's why the new interface works with system page order, instead of absolute page size: 0 means the ring buffer sub page is equal to 1 system page and so forth: 0 - 1 system page 1 - 2 system pages 2 - 4 system pages ... The ring buffer sub page size is limited between 1 and 128 system pages. The default value is 1 system page. New ring buffer APIs are introduced: ring_buffer_subbuf_order_set() ring_buffer_subbuf_order_get() ring_buffer_subbuf_size_get() Link: https://lore.kernel.org/linux-trace-devel/20211213094825.61876-4-tz.stoyanov@gmail.com Link: https://lore.kernel.org/linux-trace-kernel/20231219185628.298324722@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Kent Overstreet <kent.overstreet@gmail.com> Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Tzvetomir Stoyanov (VMware)
|
139f840021 |
ring-buffer: Page size per ring buffer
Currently the size of one sub buffer page is global for all buffers and it is hard coded to one system page. In order to introduce configurable ring buffer sub page size, the internal logic should be refactored to work with sub page size per ring buffer. Link: https://lore.kernel.org/linux-trace-devel/20211213094825.61876-3-tz.stoyanov@gmail.com Link: https://lore.kernel.org/linux-trace-kernel/20231219185628.009147038@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Kent Overstreet <kent.overstreet@gmail.com> Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Tzvetomir Stoyanov (VMware)
|
d5cfbdfc96 |
ring-buffer: Have ring_buffer_print_page_header() be able to access ring_buffer_iter
In order to introduce sub-buffer size per ring buffer, some internal refactoring is needed. As ring_buffer_print_page_header() will depend on the trace_buffer structure, it is moved after the structure definition. Link: https://lore.kernel.org/linux-trace-devel/20211213094825.61876-2-tz.stoyanov@gmail.com Link: https://lore.kernel.org/linux-trace-kernel/20231219185627.723857541@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Kent Overstreet <kent.overstreet@gmail.com> Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Steven Rostedt (Google)
|
f50345b49b |
ring-buffer: Check if absolute timestamp goes backwards
The check_buffer() which checks the timestamps of the ring buffer sub-buffer page, when enabled, only checks if the adding of deltas of the events from the last absolute timestamp or the timestamp of the sub-buffer page adds up to the current event. What it does not check is if the absolute timestamp causes the time of the events to go backwards, as that can cause issues elsewhere. Test for the timestamp going backwards too. This also fixes a slight issue where if the warning triggers at boot up (because of the resetting of the tsc), it will disable all further checks, even those that are after boot Have it continue checking if the warning was ignored during boot up. Link: https://lore.kernel.org/linux-trace-kernel/20231219074732.18b092d4@gandalf.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Steven Rostedt (Google)
|
d40dbb617a |
ring-buffer: Add interrupt information to dump of data sub-buffer
When the ring buffer timestamp verifier triggers, it dumps the content of the sub-buffer. But currently it only dumps the timestamps and the offset of the data as well as the deltas. It would be even more informative if the event data also showed the interrupt context level it was in. That is, if each event showed that the event was written in normal, softirq, irq or NMI context. Then a better idea about how the events may have been interrupted from each other. As the payload of the ring buffer is really a black box of the ring buffer, just assume that if the payload is larger than a trace entry, that it is a trace entry. As trace entries have the interrupt context information saved in a flags field, look at that location and report the output of the flags. If the payload is not a trace entry, there's no way to really know, and the information will be garbage. But that's OK, because this is for debugging only (this output is not used in production as the buffer check that calls it causes a huge overhead to the tracing). This information, when available, is crucial for debugging timestamp issues. If it's garbage, it will also be pretty obvious that its garbage too. As this output usually happens in kselftests of the tracing code, the user will know what the payload is at the time. Link: https://lore.kernel.org/linux-trace-kernel/20231219074542.6f304601@gandalf.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Suggested-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Steven Rostedt (Google)
|
c84897c0ff |
ring-buffer: Remove 32bit timestamp logic
Each event has a 27 bit timestamp delta that is used to hold the delta from the last event. If the time between events is greater than 2^27, then a timestamp is added that holds a 59 bit absolute timestamp. Until |
||
|
Steven Rostedt (Google)
|
8ec90be7f1 |
tracing: Allow for max buffer data size trace_marker writes
Allow a trace write to be as big as the ring buffer tracing data will allow. Currently, it only allows writes of 1KB in size, but there's no reason that it cannot allow what the ring buffer can hold. Link: https://lore.kernel.org/linux-trace-kernel/20231212131901.5f501e72@gandalf.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Steven Rostedt (Google)
|
0b9036efd8 |
ring-buffer: Add offset of events in dump on mismatch
On bugs that have the ring buffer timestamp get out of sync, the config CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS, that checks for it and if it is detected it causes a dump of the bad sub buffer. It shows each event and their timestamp as well as the delta in the event. But it's also good to see the offset into the subbuffer for that event to know if how close to the end it is. Also print where the last event actually ended compared to where it was expected to end. Link: https://lore.kernel.org/linux-trace-kernel/20231211131623.59eaebd2@gandalf.local.home Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Steven Rostedt (Google)
|
b803d7c664 |
ring-buffer: Fix slowpath of interrupted event
To synchronize the timestamps with the ring buffer reservation, there are
two timestamps that are saved in the buffer meta data.
1. before_stamp
2. write_stamp
When the two are equal, the write_stamp is considered valid, as in, it may
be used to calculate the delta of the next event as the write_stamp is the
timestamp of the previous reserved event on the buffer.
This is done by the following:
/*A*/ w = current position on the ring buffer
before = before_stamp
after = write_stamp
ts = read current timestamp
if (before != after) {
write_stamp is not valid, force adding an absolute
timestamp.
}
/*B*/ before_stamp = ts
/*C*/ write = local_add_return(event length, position on ring buffer)
if (w == write - event length) {
/* Nothing interrupted between A and C */
/*E*/ write_stamp = ts;
delta = ts - after
/*
* If nothing interrupted again,
* before_stamp == write_stamp and write_stamp
* can be used to calculate the delta for
* events that come in after this one.
*/
} else {
/*
* The slow path!
* Was interrupted between A and C.
*/
This is the place that there's a bug. We currently have:
after = write_stamp
ts = read current timestamp
/*F*/ if (write == current position on the ring buffer &&
after < ts && cmpxchg(write_stamp, after, ts)) {
delta = ts - after;
} else {
delta = 0;
}
The assumption is that if the current position on the ring buffer hasn't
moved between C and F, then it also was not interrupted, and that the last
event written has a timestamp that matches the write_stamp. That is the
write_stamp is valid.
But this may not be the case:
If a task context event was interrupted by softirq between B and C.
And the softirq wrote an event that got interrupted by a hard irq between
C and E.
and the hard irq wrote an event (does not need to be interrupted)
We have:
/*B*/ before_stamp = ts of normal context
---> interrupted by softirq
/*B*/ before_stamp = ts of softirq context
---> interrupted by hardirq
/*B*/ before_stamp = ts of hard irq context
/*E*/ write_stamp = ts of hard irq context
/* matches and write_stamp valid */
<----
/*E*/ write_stamp = ts of softirq context
/* No longer matches before_stamp, write_stamp is not valid! */
<---
w != write - length, go to slow path
// Right now the order of events in the ring buffer is:
//
// |-- softirq event --|-- hard irq event --|-- normal context event --|
//
after = write_stamp (this is the ts of softirq)
ts = read current timestamp
if (write == current position on the ring buffer [true] &&
after < ts [true] && cmpxchg(write_stamp, after, ts) [true]) {
delta = ts - after [Wrong!]
The delta is to be between the hard irq event and the normal context
event, but the above logic made the delta between the softirq event and
the normal context event, where the hard irq event is between the two. This
will shift all the remaining event timestamps on the sub-buffer
incorrectly.
The write_stamp is only valid if it matches the before_stamp. The cmpxchg
does nothing to help this.
Instead, the following logic can be done to fix this:
before = before_stamp
ts = read current timestamp
before_stamp = ts
after = write_stamp
if (write == current position on the ring buffer &&
after == before && after < ts) {
delta = ts - after
} else {
delta = 0;
}
The above will only use the write_stamp if it still matches before_stamp
and was tested to not have changed since C.
As a bonus, with this logic we do not need any 64-bit cmpxchg() at all!
This means the 32-bit rb_time_t workaround can finally be removed. But
that's for a later time.
Link: https://lore.kernel.org/linux-trace-kernel/20231218175229.58ec3daf@gandalf.local.home/
Link: https://lore.kernel.org/linux-trace-kernel/20231218230712.3a76b081@gandalf.local.home
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Fixes:
|
||
|
Steven Rostedt (Google)
|
712292308a |
ring-buffer: Do not record in NMI if the arch does not support cmpxchg in NMI
As the ring buffer recording requires cmpxchg() to work, if the architecture does not support cmpxchg in NMI, then do not do any recording within an NMI. Link: https://lore.kernel.org/linux-trace-kernel/20231213175403.6fc18540@gandalf.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Steven Rostedt (Google)
|
0aa0e5289c |
ring-buffer: Have rb_time_cmpxchg() set the msb counter too
The rb_time_cmpxchg() on 32-bit architectures requires setting three
32-bit words to represent the 64-bit timestamp, with some salt for
synchronization. Those are: msb, top, and bottom
The issue is, the rb_time_cmpxchg() did not properly salt the msb portion,
and the msb that was written was stale.
Link: https://lore.kernel.org/linux-trace-kernel/20231215084114.20899342@rorschach.local.home
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes:
|
||
|
Mathieu Desnoyers
|
dec890089b |
ring-buffer: Fix 32-bit rb_time_read() race with rb_time_cmpxchg()
The following race can cause rb_time_read() to observe a corrupted time
stamp:
rb_time_cmpxchg()
[...]
if (!rb_time_read_cmpxchg(&t->msb, msb, msb2))
return false;
if (!rb_time_read_cmpxchg(&t->top, top, top2))
return false;
<interrupted before updating bottom>
__rb_time_read()
[...]
do {
c = local_read(&t->cnt);
top = local_read(&t->top);
bottom = local_read(&t->bottom);
msb = local_read(&t->msb);
} while (c != local_read(&t->cnt));
*cnt = rb_time_cnt(top);
/* If top and msb counts don't match, this interrupted a write */
if (*cnt != rb_time_cnt(msb))
return false;
^ this check fails to catch that "bottom" is still not updated.
So the old "bottom" value is returned, which is wrong.
Fix this by checking that all three of msb, top, and bottom 2-bit cnt
values match.
The reason to favor checking all three fields over requiring a specific
update order for both rb_time_set() and rb_time_cmpxchg() is because
checking all three fields is more robust to handle partial failures of
rb_time_cmpxchg() when interrupted by nested rb_time_set().
Link: https://lore.kernel.org/lkml/20231211201324.652870-1-mathieu.desnoyers@efficios.com/
Link: https://lore.kernel.org/linux-trace-kernel/20231212193049.680122-1-mathieu.desnoyers@efficios.com
Fixes:
|
||
|
Steven Rostedt (Google)
|
fff88fa0fb |
ring-buffer: Fix a race in rb_time_cmpxchg() for 32 bit archs
Mathieu Desnoyers pointed out an issue in the rb_time_cmpxchg() for 32 bit
architectures. That is:
static bool rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set)
{
unsigned long cnt, top, bottom, msb;
unsigned long cnt2, top2, bottom2, msb2;
u64 val;
/* The cmpxchg always fails if it interrupted an update */
if (!__rb_time_read(t, &val, &cnt2))
return false;
if (val != expect)
return false;
<<<< interrupted here!
cnt = local_read(&t->cnt);
The problem is that the synchronization counter in the rb_time_t is read
*after* the value of the timestamp is read. That means if an interrupt
were to come in between the value being read and the counter being read,
it can change the value and the counter and the interrupted process would
be clueless about it!
The counter needs to be read first and then the value. That way it is easy
to tell if the value is stale or not. If the counter hasn't been updated,
then the value is still good.
Link: https://lore.kernel.org/linux-trace-kernel/20231211201324.652870-1-mathieu.desnoyers@efficios.com/
Link: https://lore.kernel.org/linux-trace-kernel/20231212115301.7a9c9a64@gandalf.local.home
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Fixes:
|
||
|
Steven Rostedt (Google)
|
083e9f65bd |
ring-buffer: Remove useless update to write_stamp in rb_try_to_discard()
When filtering is enabled, a temporary buffer is created to place the
content of the trace event output so that the filter logic can decide
from the trace event output if the trace event should be filtered out or
not. If it is to be filtered out, the content in the temporary buffer is
simply discarded, otherwise it is written into the trace buffer.
But if an interrupt were to come in while a previous event was using that
temporary buffer, the event written by the interrupt would actually go
into the ring buffer itself to prevent corrupting the data on the
temporary buffer. If the event is to be filtered out, the event in the
ring buffer is discarded, or if it fails to discard because another event
were to have already come in, it is turned into padding.
The update to the write_stamp in the rb_try_to_discard() happens after a
fix was made to force the next event after the discard to use an absolute
timestamp by setting the before_stamp to zero so it does not match the
write_stamp (which causes an event to use the absolute timestamp).
But there's an effort in rb_try_to_discard() to put back the write_stamp
to what it was before the event was added. But this is useless and
wasteful because nothing is going to be using that write_stamp for
calculations as it still will not match the before_stamp.
Remove this useless update, and in doing so, we remove another
cmpxchg64()!
Also update the comments to reflect this change as well as remove some
extra white space in another comment.
Link: https://lore.kernel.org/linux-trace-kernel/20231215081810.1f4f38fe@rorschach.local.home
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Vincent Donnefort <vdonnefort@google.com>
Fixes:
|
||
|
Steven Rostedt (Google)
|
dd93942570 |
ring-buffer: Do not try to put back write_stamp
If an update to an event is interrupted by another event between the time
the initial event allocated its buffer and where it wrote to the
write_stamp, the code try to reset the write stamp back to the what it had
just overwritten. It knows that it was overwritten via checking the
before_stamp, and if it didn't match what it wrote to the before_stamp
before it allocated its space, it knows it was overwritten.
To put back the write_stamp, it uses the before_stamp it read. The problem
here is that by writing the before_stamp to the write_stamp it makes the
two equal again, which means that the write_stamp can be considered valid
as the last timestamp written to the ring buffer. But this is not
necessarily true. The event that interrupted the event could have been
interrupted in a way that it was interrupted as well, and can end up
leaving with an invalid write_stamp. But if this happens and returns to
this context that uses the before_stamp to update the write_stamp again,
it can possibly incorrectly make it valid, causing later events to have in
correct time stamps.
As it is OK to leave this function with an invalid write_stamp (one that
doesn't match the before_stamp), there's no reason to try to make it valid
again in this case. If this race happens, then just leave with the invalid
write_stamp and the next event to come along will just add a absolute
timestamp and validate everything again.
Bonus points: This gets rid of another cmpxchg64!
Link: https://lore.kernel.org/linux-trace-kernel/20231214222921.193037a7@gandalf.local.home
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Vincent Donnefort <vdonnefort@google.com>
Fixes:
|
||
|
Steven Rostedt (Google)
|
b049525855 |
ring-buffer: Have saved event hold the entire event
For the ring buffer iterator (non-consuming read), the event needs to be
copied into the iterator buffer to make sure that a writer does not
overwrite it while the user is reading it. If a write happens during the
copy, the buffer is simply discarded.
But the temp buffer itself was not big enough. The allocation of the
buffer was only BUF_MAX_DATA_SIZE, which is the maximum data size that can
be passed into the ring buffer and saved. But the temp buffer needs to
hold the meta data as well. That would be BUF_PAGE_SIZE and not
BUF_MAX_DATA_SIZE.
Link: https://lore.kernel.org/linux-trace-kernel/20231212072558.61f76493@gandalf.local.home
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes:
|
||
|
Steven Rostedt (Google)
|
9e45e39dc2 |
ring-buffer: Do not update before stamp when switching sub-buffers
The ring buffer timestamps are synchronized by two timestamp placeholders.
One is the "before_stamp" and the other is the "write_stamp" (sometimes
referred to as the "after stamp" but only in the comments. These two
stamps are key to knowing how to handle nested events coming in with a
lockless system.
When moving across sub-buffers, the before stamp is updated but the write
stamp is not. There's an effort to put back the before stamp to something
that seems logical in case there's nested events. But as the current event
is about to cross sub-buffers, and so will any new nested event that happens,
updating the before stamp is useless, and could even introduce new race
conditions.
The first event on a sub-buffer simply uses the sub-buffer's timestamp
and keeps a "delta" of zero. The "before_stamp" and "write_stamp" are not
used in the algorithm in this case. There's no reason to try to fix the
before_stamp when this happens.
As a bonus, it removes a cmpxchg() when crossing sub-buffers!
Link: https://lore.kernel.org/linux-trace-kernel/20231211114420.36dde01b@gandalf.local.home
Cc: stable@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes:
|
||
|
Steven Rostedt (Google)
|
17d8017581 |
ring-buffer: Fix memory leak of free page
Reading the ring buffer does a swap of a sub-buffer within the ring buffer
with a empty sub-buffer. This allows the reader to have full access to the
content of the sub-buffer that was swapped out without having to worry
about contention with the writer.
The readers call ring_buffer_alloc_read_page() to allocate a page that
will be used to swap with the ring buffer. When the code is finished with
the reader page, it calls ring_buffer_free_read_page(). Instead of freeing
the page, it stores it as a spare. Then next call to
ring_buffer_alloc_read_page() will return this spare instead of calling
into the memory management system to allocate a new page.
Unfortunately, on freeing of the ring buffer, this spare page is not
freed, and causes a memory leak.
Link: https://lore.kernel.org/linux-trace-kernel/20231210221250.7b9cc83c@rorschach.local.home
Cc: stable@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes:
|
||
|
Steven Rostedt (Google)
|
b3ae7b67b8 |
ring-buffer: Fix writing to the buffer with max_data_size
The maximum ring buffer data size is the maximum size of data that can be recorded on the ring buffer. Events must be smaller than the sub buffer data size minus any meta data. This size is checked before trying to allocate from the ring buffer because the allocation assumes that the size will fit on the sub buffer. The maximum size was calculated as the size of a sub buffer page (which is currently PAGE_SIZE minus the sub buffer header) minus the size of the meta data of an individual event. But it missed the possible adding of a time stamp for events that are added long enough apart that the event meta data can't hold the time delta. When an event is added that is greater than the current BUF_MAX_DATA_SIZE minus the size of a time stamp, but still less than or equal to BUF_MAX_DATA_SIZE, the ring buffer would go into an infinite loop, looking for a page that can hold the event. Luckily, there's a check for this loop and after 1000 iterations and a warning is emitted and the ring buffer is disabled. But this should never happen. This can happen when a large event is added first, or after a long period where an absolute timestamp is prefixed to the event, increasing its size by 8 bytes. This passes the check and then goes into the algorithm that causes the infinite loop. For events that are the first event on the sub-buffer, it does not need to add a timestamp, because the sub-buffer itself contains an absolute timestamp, and adding one is redundant. The fix is to check if the event is to be the first event on the sub-buffer, and if it is, then do not add a timestamp. This also fixes 32 bit adding a timestamp when a read of before_stamp or write_stamp is interrupted. There's still no need to add that timestamp if the event is going to be the first event on the sub buffer. Also, if the buffer has "time_stamp_abs" set, then also check if the length plus the timestamp is greater than the BUF_MAX_DATA_SIZE. Link: https://lore.kernel.org/all/20231212104549.58863438@gandalf.local.home/ Link: https://lore.kernel.org/linux-trace-kernel/20231212071837.5fdd6c13@gandalf.local.home Link: https://lore.kernel.org/linux-trace-kernel/20231212111617.39e02849@gandalf.local.home Cc: stable@vger.kernel.org Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Fixes: |
||
|
Steven Rostedt (Google)
|
f458a14534 |
ring-buffer: Test last update in 32bit version of __rb_time_read()
Since 64 bit cmpxchg() is very expensive on 32bit architectures, the
timestamp used by the ring buffer does some interesting tricks to be able
to still have an atomic 64 bit number. It originally just used 60 bits and
broke it up into two 32 bit words where the extra 2 bits were used for
synchronization. But this was not enough for all use cases, and all 64
bits were required.
The 32bit version of the ring buffer timestamp was then broken up into 3
32bit words using the same counter trick. But one update was not done. The
check to see if the read operation was done without interruption only
checked the first two words and not last one (like it had before this
update). Fix it by making sure all three updates happen without
interruption by comparing the initial counter with the last updated
counter.
Link: https://lore.kernel.org/linux-trace-kernel/20231206100050.3100b7bb@gandalf.local.home
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes:
|
||
|
Steven Rostedt (Google)
|
b2dd797543 |
ring-buffer: Force absolute timestamp on discard of event
There's a race where if an event is discarded from the ring buffer and an
interrupt were to happen at that time and insert an event, the time stamp
is still used from the discarded event as an offset. This can screw up the
timings.
If the event is going to be discarded, set the "before_stamp" to zero.
When a new event comes in, it compares the "before_stamp" with the
"write_stamp" and if they are not equal, it will insert an absolute
timestamp. This will prevent the timings from getting out of sync due to
the discarded event.
Link: https://lore.kernel.org/linux-trace-kernel/20231206100244.5130f9b3@gandalf.local.home
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes:
|
||
|
Uros Bizjak
|
bdf4fb6280 |
ring_buffer: Use try_cmpxchg instead of cmpxchg in rb_insert_pages
Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in rb_insert_pages. x86 CMPXCHG instruction returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg). No functional change intended. Link: https://lore.kernel.org/linux-trace-kernel/20230914163420.12923-1-ubizjak@gmail.com Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Steven Rostedt (Google)
|
1e0cb399c7 |
ring-buffer: Update "shortest_full" in polling
It was discovered that the ring buffer polling was incorrectly stating that read would not block, but that's because polling did not take into account that reads will block if the "buffer-percent" was set. Instead, the ring buffer polling would say reads would not block if there was any data in the ring buffer. This was incorrect behavior from a user space point of view. This was fixed by commit |
||
|
Zheng Yejian
|
45d99ea451 |
ring-buffer: Fix bytes info in per_cpu buffer stats
The 'bytes' info in file 'per_cpu/cpu<X>/stats' means the number of
bytes in cpu buffer that have not been consumed. However, currently
after consuming data by reading file 'trace_pipe', the 'bytes' info
was not changed as expected.
# cat per_cpu/cpu0/stats
entries: 0
overrun: 0
commit overrun: 0
bytes: 568 <--- 'bytes' is problematical !!!
oldest event ts: 8651.371479
now ts: 8653.912224
dropped events: 0
read events: 8
The root cause is incorrect stat on cpu_buffer->read_bytes. To fix it:
1. When stat 'read_bytes', account consumed event in rb_advance_reader();
2. When stat 'entries_bytes', exclude the discarded padding event which
is smaller than minimum size because it is invisible to reader. Then
use rb_page_commit() instead of BUF_PAGE_SIZE at where accounting for
page-based read/remove/overrun.
Also correct the comments of ring_buffer_bytes_cpu() in this patch.
Link: https://lore.kernel.org/linux-trace-kernel/20230921125425.1708423-1-zhengyejian1@huawei.com
Cc: stable@vger.kernel.org
Fixes:
|
||
|
Steven Rostedt (Google)
|
95a404bd60 |
ring-buffer: Do not attempt to read past "commit"
When iterating over the ring buffer while the ring buffer is active, the writer can corrupt the reader. There's barriers to help detect this and handle it, but that code missed the case where the last event was at the very end of the page and has only 4 bytes left. The checks to detect the corruption by the writer to reads needs to see the length of the event. If the length in the first 4 bytes is zero then the length is stored in the second 4 bytes. But if the writer is in the process of updating that code, there's a small window where the length in the first 4 bytes could be zero even though the length is only 4 bytes. That will cause rb_event_length() to read the next 4 bytes which could happen to be off the allocated page. To protect against this, fail immediately if the next event pointer is less than 8 bytes from the end of the commit (last byte of data), as all events must be a minimum of 8 bytes anyway. Link: https://lore.kernel.org/all/20230905141245.26470-1-Tze-nan.Wu@mediatek.com/ Link: https://lore.kernel.org/linux-trace-kernel/20230907122820.0899019c@gandalf.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Reported-by: Tze-nan Wu <Tze-nan.Wu@mediatek.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Zheng Yejian
|
f6bd2c9248 |
ring-buffer: Avoid softlockup in ring_buffer_resize()
When user resize all trace ring buffer through file 'buffer_size_kb', then in ring_buffer_resize(), kernel allocates buffer pages for each cpu in a loop. If the kernel preemption model is PREEMPT_NONE and there are many cpus and there are many buffer pages to be allocated, it may not give up cpu for a long time and finally cause a softlockup. To avoid it, call cond_resched() after each cpu buffer allocation. Link: https://lore.kernel.org/linux-trace-kernel/20230906081930.3939106-1-zhengyejian1@huawei.com Cc: <mhiramat@kernel.org> Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Uros Bizjak
|
00a8478f8f |
ring_buffer: Use try_cmpxchg instead of cmpxchg
Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in ring_buffer.c. x86 CMPXCHG instruction returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg). No functional change intended. Link: https://lore.kernel.org/linux-trace-kernel/20230714154418.8884-1-ubizjak@gmail.com Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Gaosheng Cui
|
151e34d1c6 |
ring-buffer: Fix kernel-doc warnings in ring_buffer.c
Fix kernel-doc warnings: kernel/trace/ring_buffer.c:954: warning: Function parameter or member 'cpu' not described in 'ring_buffer_wake_waiters' kernel/trace/ring_buffer.c:3383: warning: Excess function parameter 'event' description in 'ring_buffer_unlock_commit' kernel/trace/ring_buffer.c:5359: warning: Excess function parameter 'cpu' description in 'ring_buffer_reset_online_cpus' Link: https://lkml.kernel.org/r/20230724140827.1023266-2-cuigaosheng1@huawei.com Cc: <mhiramat@kernel.org> Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Zheng Yejian
|
2d093282b0 |
ring-buffer: Fix wrong stat of cpu_buffer->read
When pages are removed in rb_remove_pages(), 'cpu_buffer->read' is set
to 0 in order to make sure any read iterators reset themselves. However,
this will mess 'entries' stating, see following steps:
# cd /sys/kernel/tracing/
# 1. Enlarge ring buffer prepare for later reducing:
# echo 20 > per_cpu/cpu0/buffer_size_kb
# 2. Write a log into ring buffer of cpu0:
# taskset -c 0 echo "hello1" > trace_marker
# 3. Read the log:
# cat per_cpu/cpu0/trace_pipe
<...>-332 [000] ..... 62.406844: tracing_mark_write: hello1
# 4. Stop reading and see the stats, now 0 entries, and 1 event readed:
# cat per_cpu/cpu0/stats
entries: 0
[...]
read events: 1
# 5. Reduce the ring buffer
# echo 7 > per_cpu/cpu0/buffer_size_kb
# 6. Now entries became unexpected 1 because actually no entries!!!
# cat per_cpu/cpu0/stats
entries: 1
[...]
read events: 0
To fix it, introduce 'page_removed' field to count total removed pages
since last reset, then use it to let read iterators reset themselves
instead of changing the 'read' pointer.
Link: https://lore.kernel.org/linux-trace-kernel/20230724054040.3489499-1-zhengyejian1@huawei.com
Cc: <mhiramat@kernel.org>
Cc: <vnagarnaik@google.com>
Fixes:
|
||
|
Chen Lin
|
8a96c0288d |
ring-buffer: Do not swap cpu_buffer during resize process
When ring_buffer_swap_cpu was called during resize process,
the cpu buffer was swapped in the middle, resulting in incorrect state.
Continuing to run in the wrong state will result in oops.
This issue can be easily reproduced using the following two scripts:
/tmp # cat test1.sh
//#! /bin/sh
for i in `seq 0 100000`
do
echo 2000 > /sys/kernel/debug/tracing/buffer_size_kb
sleep 0.5
echo 5000 > /sys/kernel/debug/tracing/buffer_size_kb
sleep 0.5
done
/tmp # cat test2.sh
//#! /bin/sh
for i in `seq 0 100000`
do
echo irqsoff > /sys/kernel/debug/tracing/current_tracer
sleep 1
echo nop > /sys/kernel/debug/tracing/current_tracer
sleep 1
done
/tmp # ./test1.sh &
/tmp # ./test2.sh &
A typical oops log is as follows, sometimes with other different oops logs.
[ 231.711293] WARNING: CPU: 0 PID: 9 at kernel/trace/ring_buffer.c:2026 rb_update_pages+0x378/0x3f8
[ 231.713375] Modules linked in:
[ 231.714735] CPU: 0 PID: 9 Comm: kworker/0:1 Tainted: G W 6.5.0-rc1-00276-g20edcec23f92 #15
[ 231.716750] Hardware name: linux,dummy-virt (DT)
[ 231.718152] Workqueue: events update_pages_handler
[ 231.719714] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 231.721171] pc : rb_update_pages+0x378/0x3f8
[ 231.722212] lr : rb_update_pages+0x25c/0x3f8
[ 231.723248] sp : ffff800082b9bd50
[ 231.724169] x29: ffff800082b9bd50 x28: ffff8000825f7000 x27: 0000000000000000
[ 231.726102] x26: 0000000000000001 x25: fffffffffffff010 x24: 0000000000000ff0
[ 231.728122] x23: ffff0000c3a0b600 x22: ffff0000c3a0b5c0 x21: fffffffffffffe0a
[ 231.730203] x20: ffff0000c3a0b600 x19: ffff0000c0102400 x18: 0000000000000000
[ 231.732329] x17: 0000000000000000 x16: 0000000000000000 x15: 0000ffffe7aa8510
[ 231.734212] x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000002
[ 231.736291] x11: ffff8000826998a8 x10: ffff800082b9baf0 x9 : ffff800081137558
[ 231.738195] x8 : fffffc00030e82c8 x7 : 0000000000000000 x6 : 0000000000000001
[ 231.740192] x5 : ffff0000ffbafe00 x4 : 0000000000000000 x3 : 0000000000000000
[ 231.742118] x2 : 00000000000006aa x1 : 0000000000000001 x0 : ffff0000c0007208
[ 231.744196] Call trace:
[ 231.744892] rb_update_pages+0x378/0x3f8
[ 231.745893] update_pages_handler+0x1c/0x38
[ 231.746893] process_one_work+0x1f0/0x468
[ 231.747852] worker_thread+0x54/0x410
[ 231.748737] kthread+0x124/0x138
[ 231.749549] ret_from_fork+0x10/0x20
[ 231.750434] ---[ end trace 0000000000000000 ]---
[ 233.720486] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
[ 233.721696] Mem abort info:
[ 233.721935] ESR = 0x0000000096000004
[ 233.722283] EC = 0x25: DABT (current EL), IL = 32 bits
[ 233.722596] SET = 0, FnV = 0
[ 233.722805] EA = 0, S1PTW = 0
[ 233.723026] FSC = 0x04: level 0 translation fault
[ 233.723458] Data abort info:
[ 233.723734] ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000
[ 233.724176] CM = 0, WnR = 0, TnD = 0, TagAccess = 0
[ 233.724589] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
[ 233.725075] user pgtable: 4k pages, 48-bit VAs, pgdp=0000000104943000
[ 233.725592] [0000000000000000] pgd=0000000000000000, p4d=0000000000000000
[ 233.726231] Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
[ 233.726720] Modules linked in:
[ 233.727007] CPU: 0 PID: 9 Comm: kworker/0:1 Tainted: G W 6.5.0-rc1-00276-g20edcec23f92 #15
[ 233.727777] Hardware name: linux,dummy-virt (DT)
[ 233.728225] Workqueue: events update_pages_handler
[ 233.728655] pstate: 200000c5 (nzCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 233.729054] pc : rb_update_pages+0x1a8/0x3f8
[ 233.729334] lr : rb_update_pages+0x154/0x3f8
[ 233.729592] sp : ffff800082b9bd50
[ 233.729792] x29: ffff800082b9bd50 x28: ffff8000825f7000 x27: 0000000000000000
[ 233.730220] x26: 0000000000000000 x25: ffff800082a8b840 x24: ffff0000c0102418
[ 233.730653] x23: 0000000000000000 x22: fffffc000304c880 x21: 0000000000000003
[ 233.731105] x20: 00000000000001f4 x19: ffff0000c0102400 x18: ffff800082fcbc58
[ 233.731727] x17: 0000000000000000 x16: 0000000000000001 x15: 0000000000000001
[ 233.732282] x14: ffff8000825fe0c8 x13: 0000000000000001 x12: 0000000000000000
[ 233.732709] x11: ffff8000826998a8 x10: 0000000000000ae0 x9 : ffff8000801b760c
[ 233.733148] x8 : fefefefefefefeff x7 : 0000000000000018 x6 : ffff0000c03298c0
[ 233.733553] x5 : 0000000000000002 x4 : 0000000000000000 x3 : 0000000000000000
[ 233.733972] x2 : ffff0000c3a0b600 x1 : 0000000000000000 x0 : 0000000000000000
[ 233.734418] Call trace:
[ 233.734593] rb_update_pages+0x1a8/0x3f8
[ 233.734853] update_pages_handler+0x1c/0x38
[ 233.735148] process_one_work+0x1f0/0x468
[ 233.735525] worker_thread+0x54/0x410
[ 233.735852] kthread+0x124/0x138
[ 233.736064] ret_from_fork+0x10/0x20
[ 233.736387] Code: 92400000 910006b5 aa000021 aa0303f7 (f9400060)
[ 233.736959] ---[ end trace 0000000000000000 ]---
After analysis, the seq of the error is as follows [1-5]:
int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
int cpu_id)
{
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
//1. get cpu_buffer, aka cpu_buffer(A)
...
...
schedule_work_on(cpu,
&cpu_buffer->update_pages_work);
//2. 'update_pages_work' is queue on 'cpu', cpu_buffer(A) is passed to
// update_pages_handler, do the update process, set 'update_done' in
// complete(&cpu_buffer->update_done) and to wakeup resize process.
//---->
//3. Just at this moment, ring_buffer_swap_cpu is triggered,
//cpu_buffer(A) be swaped to cpu_buffer(B), the max_buffer.
//ring_buffer_swap_cpu is called as the 'Call trace' below.
Call trace:
dump_backtrace+0x0/0x2f8
show_stack+0x18/0x28
dump_stack+0x12c/0x188
ring_buffer_swap_cpu+0x2f8/0x328
update_max_tr_single+0x180/0x210
check_critical_timing+0x2b4/0x2c8
tracer_hardirqs_on+0x1c0/0x200
trace_hardirqs_on+0xec/0x378
el0_svc_common+0x64/0x260
do_el0_svc+0x90/0xf8
el0_svc+0x20/0x30
el0_sync_handler+0xb0/0xb8
el0_sync+0x180/0x1c0
//<----
/* wait for all the updates to complete */
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
//4. get cpu_buffer, cpu_buffer(B) is used in the following process,
//the state of cpu_buffer(A) and cpu_buffer(B) is totally wrong.
//for example, cpu_buffer(A)->update_done will leave be set 1, and will
//not 'wait_for_completion' at the next resize round.
if (!cpu_buffer->nr_pages_to_update)
continue;
if (cpu_online(cpu))
wait_for_completion(&cpu_buffer->update_done);
cpu_buffer->nr_pages_to_update = 0;
}
...
}
//5. the state of cpu_buffer(A) and cpu_buffer(B) is totally wrong,
//Continuing to run in the wrong state, then oops occurs.
Link: https://lore.kernel.org/linux-trace-kernel/202307191558478409990@zte.com.cn
Signed-off-by: Chen Lin <chen.lin5@zte.com.cn>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
|
||
|
Zheng Yejian
|
7e42907f3a |
ring-buffer: Fix deadloop issue on reading trace_pipe
Soft lockup occurs when reading file 'trace_pipe':
watchdog: BUG: soft lockup - CPU#6 stuck for 22s! [cat:4488]
[...]
RIP: 0010:ring_buffer_empty_cpu+0xed/0x170
RSP: 0018:ffff88810dd6fc48 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000246 RCX: ffffffff93d1aaeb
RDX: ffff88810a280040 RSI: 0000000000000008 RDI: ffff88811164b218
RBP: ffff88811164b218 R08: 0000000000000000 R09: ffff88815156600f
R10: ffffed102a2acc01 R11: 0000000000000001 R12: 0000000051651901
R13: 0000000000000000 R14: ffff888115e49500 R15: 0000000000000000
[...]
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8d853c2000 CR3: 000000010dcd8000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
__find_next_entry+0x1a8/0x4b0
? peek_next_entry+0x250/0x250
? down_write+0xa5/0x120
? down_write_killable+0x130/0x130
trace_find_next_entry_inc+0x3b/0x1d0
tracing_read_pipe+0x423/0xae0
? tracing_splice_read_pipe+0xcb0/0xcb0
vfs_read+0x16b/0x490
ksys_read+0x105/0x210
? __ia32_sys_pwrite64+0x200/0x200
? switch_fpu_return+0x108/0x220
do_syscall_64+0x33/0x40
entry_SYSCALL_64_after_hwframe+0x61/0xc6
Through the vmcore, I found it's because in tracing_read_pipe(),
ring_buffer_empty_cpu() found some buffer is not empty but then it
cannot read anything due to "rb_num_of_entries() == 0" always true,
Then it infinitely loop the procedure due to user buffer not been
filled, see following code path:
tracing_read_pipe() {
... ...
waitagain:
tracing_wait_pipe() // 1. find non-empty buffer here
trace_find_next_entry_inc() // 2. loop here try to find an entry
__find_next_entry()
ring_buffer_empty_cpu(); // 3. find non-empty buffer
peek_next_entry() // 4. but peek always return NULL
ring_buffer_peek()
rb_buffer_peek()
rb_get_reader_page()
// 5. because rb_num_of_entries() == 0 always true here
// then return NULL
// 6. user buffer not been filled so goto 'waitgain'
// and eventually leads to an deadloop in kernel!!!
}
By some analyzing, I found that when resetting ringbuffer, the 'entries'
of its pages are not all cleared (see rb_reset_cpu()). Then when reducing
the ringbuffer, and if some reduced pages exist dirty 'entries' data, they
will be added into 'cpu_buffer->overrun' (see rb_remove_pages()), which
cause wrong 'overrun' count and eventually cause the deadloop issue.
To fix it, we need to clear every pages in rb_reset_cpu().
Link: https://lore.kernel.org/linux-trace-kernel/20230708225144.3785600-1-zhengyejian1@huawei.com
Cc: stable@vger.kernel.org
Fixes:
|
||
|
Linus Torvalds
|
d579c468d7 |
tracing updates for 6.4:
- User events are finally ready!
After lots of collaboration between various parties, we finally locked
down on a stable interface for user events that can also work with user
space only tracing. This is implemented by telling the kernel (or user
space library, but that part is user space only and not part of this
patch set), where the variable is that the application uses to know if
something is listening to the trace. There's also an interface to tell
the kernel about these events, which will show up in the
/sys/kernel/tracing/events/user_events/ directory, where it can be
enabled. When it's enabled, the kernel will update the variable, to tell
the application to start writing to the kernel.
See https://lwn.net/Articles/927595/
- Cleaned up the direct trampolines code to simplify arm64 addition of
direct trampolines. Direct trampolines use the ftrace interface but
instead of jumping to the ftrace trampoline, applications (mostly BPF)
can register their own trampoline for performance reasons.
- Some updates to the fprobe infrastructure. fprobes are more efficient than
kprobes, as it does not need to save all the registers that kprobes on
ftrace do. More work needs to be done before the fprobes will be exposed
as dynamic events.
- More updates to references to the obsolete path of
/sys/kernel/debug/tracing for the new /sys/kernel/tracing path.
- Add a seq_buf_do_printk() helper to seq_bufs, to print a large buffer line
by line instead of all at once. There's users in production kernels that
have a large data dump that originally used printk() directly, but the
data dump was larger than what printk() allowed as a single print.
Using seq_buf() to do the printing fixes that.
- Add /sys/kernel/tracing/touched_functions that shows all functions that
was every traced by ftrace or a direct trampoline. This is used for
debugging issues where a traced function could have caused a crash by
a bpf program or live patching.
- Add a "fields" option that is similar to "raw" but outputs the fields of
the events. It's easier to read by humans.
- Some minor fixes and clean ups.
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Merge tag 'trace-v6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull tracing updates from Steven Rostedt:
- User events are finally ready!
After lots of collaboration between various parties, we finally
locked down on a stable interface for user events that can also work
with user space only tracing.
This is implemented by telling the kernel (or user space library, but
that part is user space only and not part of this patch set), where
the variable is that the application uses to know if something is
listening to the trace.
There's also an interface to tell the kernel about these events,
which will show up in the /sys/kernel/tracing/events/user_events/
directory, where it can be enabled.
When it's enabled, the kernel will update the variable, to tell the
application to start writing to the kernel.
See https://lwn.net/Articles/927595/
- Cleaned up the direct trampolines code to simplify arm64 addition of
direct trampolines.
Direct trampolines use the ftrace interface but instead of jumping to
the ftrace trampoline, applications (mostly BPF) can register their
own trampoline for performance reasons.
- Some updates to the fprobe infrastructure. fprobes are more efficient
than kprobes, as it does not need to save all the registers that
kprobes on ftrace do. More work needs to be done before the fprobes
will be exposed as dynamic events.
- More updates to references to the obsolete path of
/sys/kernel/debug/tracing for the new /sys/kernel/tracing path.
- Add a seq_buf_do_printk() helper to seq_bufs, to print a large buffer
line by line instead of all at once.
There are users in production kernels that have a large data dump
that originally used printk() directly, but the data dump was larger
than what printk() allowed as a single print.
Using seq_buf() to do the printing fixes that.
- Add /sys/kernel/tracing/touched_functions that shows all functions
that was every traced by ftrace or a direct trampoline. This is used
for debugging issues where a traced function could have caused a
crash by a bpf program or live patching.
- Add a "fields" option that is similar to "raw" but outputs the fields
of the events. It's easier to read by humans.
- Some minor fixes and clean ups.
* tag 'trace-v6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (41 commits)
ring-buffer: Sync IRQ works before buffer destruction
tracing: Add missing spaces in trace_print_hex_seq()
ring-buffer: Ensure proper resetting of atomic variables in ring_buffer_reset_online_cpus
recordmcount: Fix memory leaks in the uwrite function
tracing/user_events: Limit max fault-in attempts
tracing/user_events: Prevent same address and bit per process
tracing/user_events: Ensure bit is cleared on unregister
tracing/user_events: Ensure write index cannot be negative
seq_buf: Add seq_buf_do_printk() helper
tracing: Fix print_fields() for __dyn_loc/__rel_loc
tracing/user_events: Set event filter_type from type
ring-buffer: Clearly check null ptr returned by rb_set_head_page()
tracing: Unbreak user events
tracing/user_events: Use print_format_fields() for trace output
tracing/user_events: Align structs with tabs for readability
tracing/user_events: Limit global user_event count
tracing/user_events: Charge event allocs to cgroups
tracing/user_events: Update documentation for ABI
tracing/user_events: Use write ABI in example
tracing/user_events: Add ABI self-test
...
|
||
|
Johannes Berg
|
675751bb20 |
ring-buffer: Sync IRQ works before buffer destruction
If something was written to the buffer just before destruction,
it may be possible (maybe not in a real system, but it did
happen in ARCH=um with time-travel) to destroy the ringbuffer
before the IRQ work ran, leading this KASAN report (or a crash
without KASAN):
BUG: KASAN: slab-use-after-free in irq_work_run_list+0x11a/0x13a
Read of size 8 at addr 000000006d640a48 by task swapper/0
CPU: 0 PID: 0 Comm: swapper Tainted: G W O 6.3.0-rc1 #7
Stack:
60c4f20f 0c203d48 41b58ab3 60f224fc
600477fa 60f35687 60c4f20f 601273dd
00000008 6101eb00 6101eab0 615be548
Call Trace:
[<60047a58>] show_stack+0x25e/0x282
[<60c609e0>] dump_stack_lvl+0x96/0xfd
[<60c50d4c>] print_report+0x1a7/0x5a8
[<603078d3>] kasan_report+0xc1/0xe9
[<60308950>] __asan_report_load8_noabort+0x1b/0x1d
[<60232844>] irq_work_run_list+0x11a/0x13a
[<602328b4>] irq_work_tick+0x24/0x34
[<6017f9dc>] update_process_times+0x162/0x196
[<6019f335>] tick_sched_handle+0x1a4/0x1c3
[<6019fd9e>] tick_sched_timer+0x79/0x10c
[<601812b9>] __hrtimer_run_queues.constprop.0+0x425/0x695
[<60182913>] hrtimer_interrupt+0x16c/0x2c4
[<600486a3>] um_timer+0x164/0x183
[...]
Allocated by task 411:
save_stack_trace+0x99/0xb5
stack_trace_save+0x81/0x9b
kasan_save_stack+0x2d/0x54
kasan_set_track+0x34/0x3e
kasan_save_alloc_info+0x25/0x28
____kasan_kmalloc+0x8b/0x97
__kasan_kmalloc+0x10/0x12
__kmalloc+0xb2/0xe8
load_elf_phdrs+0xee/0x182
[...]
The buggy address belongs to the object at 000000006d640800
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 584 bytes inside of
freed 1024-byte region [000000006d640800, 000000006d640c00)
Add the appropriate irq_work_sync() so the work finishes before
the buffers are destroyed.
Prior to the commit in the Fixes tag below, there was only a
single global IRQ work, so this issue didn't exist.
Link: https://lore.kernel.org/linux-trace-kernel/20230427175920.a76159263122.I8295e405c44362a86c995e9c2c37e3e03810aa56@changeid
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Fixes:
|
||
|
Tze-nan Wu
|
7c339fb4d8 |
ring-buffer: Ensure proper resetting of atomic variables in ring_buffer_reset_online_cpus
In ring_buffer_reset_online_cpus, the buffer_size_kb write operation
may permanently fail if the cpu_online_mask changes between two
for_each_online_buffer_cpu loops. The number of increases and decreases
on both cpu_buffer->resize_disabled and cpu_buffer->record_disabled may be
inconsistent, causing some CPUs to have non-zero values for these atomic
variables after the function returns.
This issue can be reproduced by "echo 0 > trace" while hotplugging cpu.
After reproducing success, we can find out buffer_size_kb will not be
functional anymore.
To prevent leaving 'resize_disabled' and 'record_disabled' non-zero after
ring_buffer_reset_online_cpus returns, we ensure that each atomic variable
has been set up before atomic_sub() to it.
Link: https://lore.kernel.org/linux-trace-kernel/20230426062027.17451-1-Tze-nan.Wu@mediatek.com
Cc: stable@vger.kernel.org
Cc: <mhiramat@kernel.org>
Cc: npiggin@gmail.com
Fixes:
|
||
|
Zheng Yejian
|
625ed52717 |
ring-buffer: Clearly check null ptr returned by rb_set_head_page()
In error case, 'buffer_page' returned by rb_set_head_page() is NULL, currently check '&buffer_page->list' is equivalent to check 'buffer_page' due to 'list' is the first member of 'buffer_page', but suppose it is not some time, 'head_page' would be wild memory while check would be bypassed. Link: https://lore.kernel.org/linux-trace-kernel/20230414071729.57312-1-zhengyejian1@huawei.com Cc: <mhiramat@kernel.org> Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Zheng Yejian
|
6455b6163d |
ring-buffer: Fix race while reader and writer are on the same page
When user reads file 'trace_pipe', kernel keeps printing following logs
that warn at "cpu_buffer->reader_page->read > rb_page_size(reader)" in
rb_get_reader_page(). It just looks like there's an infinite loop in
tracing_read_pipe(). This problem occurs several times on arm64 platform
when testing v5.10 and below.
Call trace:
rb_get_reader_page+0x248/0x1300
rb_buffer_peek+0x34/0x160
ring_buffer_peek+0xbc/0x224
peek_next_entry+0x98/0xbc
__find_next_entry+0xc4/0x1c0
trace_find_next_entry_inc+0x30/0x94
tracing_read_pipe+0x198/0x304
vfs_read+0xb4/0x1e0
ksys_read+0x74/0x100
__arm64_sys_read+0x24/0x30
el0_svc_common.constprop.0+0x7c/0x1bc
do_el0_svc+0x2c/0x94
el0_svc+0x20/0x30
el0_sync_handler+0xb0/0xb4
el0_sync+0x160/0x180
Then I dump the vmcore and look into the problematic per_cpu ring_buffer,
I found that tail_page/commit_page/reader_page are on the same page while
reader_page->read is obviously abnormal:
tail_page == commit_page == reader_page == {
.write = 0x100d20,
.read = 0x8f9f4805, // Far greater than 0xd20, obviously abnormal!!!
.entries = 0x10004c,
.real_end = 0x0,
.page = {
.time_stamp = 0x857257416af0,
.commit = 0xd20, // This page hasn't been full filled.
// .data[0...0xd20] seems normal.
}
}
The root cause is most likely the race that reader and writer are on the
same page while reader saw an event that not fully committed by writer.
To fix this, add memory barriers to make sure the reader can see the
content of what is committed. Since commit
|
||
|
Uros Bizjak
|
8328e36da9 |
ring_buffer: Use try_cmpxchg instead of cmpxchg
Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old. x86 CMPXCHG instruction returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg). Also, try_cmpxchg implicitly assigns old *ptr value to "old" when cmpxchg fails. There is no need to re-read the value in the loop. No functional change intended. Link: https://lkml.kernel.org/r/20230305155532.5549-4-ubizjak@gmail.com Cc: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Acked-by: Mukesh Ojha <quic_mojha@quicinc.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Uros Bizjak
|
bc92b9562a |
ring_buffer: Change some static functions to bool
The return values of some functions are of boolean type. Change the type of these function to bool and adjust their return values. Also change type of some internal varibles to bool. No functional change intended. Link: https://lkml.kernel.org/r/20230305155532.5549-3-ubizjak@gmail.com Cc: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Reviewed-by: Mukesh Ojha <quic_mojha@quicinc.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Uros Bizjak
|
b4b55dfd96 |
ring_buffer: Change some static functions to void
The results of some static functions are not used. Change the type of these function to void and remove unnecessary returns. No functional change intended. Link: https://lkml.kernel.org/r/20230305155532.5549-2-ubizjak@gmail.com Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org> Reviewed-by: Mukesh Ojha <quic_mojha@quicinc.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Linus Torvalds
|
eaba52d63b |
Tracing fixes for 6.3:
- Fix setting affinity of hwlat threads in containers
Using sched_set_affinity() has unwanted side effects when being
called within a container. Use set_cpus_allowed_ptr() instead.
- Fix per cpu thread management of the hwlat tracer
* Do not start per_cpu threads if one is already running for the CPU.
* When starting per_cpu threads, do not clear the kthread variable
as it may already be set to running per cpu threads
- Fix return value for test_gen_kprobe_cmd()
On error the return value was overwritten by being set to
the result of the call from kprobe_event_delete(), which would
likely succeed, and thus have the function return success.
- Fix splice() reads from the trace file that was broken by
|
||
|
Vlastimil Babka
|
a98151ad53 |
ring-buffer: remove obsolete comment for free_buffer_page()
The comment refers to mm/slob.c which is being removed. It comes from commit |
||
|
Linus Torvalds
|
b72b5fecc1 |
tracing updates for 6.3:
- Add function names as a way to filter function addresses - Add sample module to test ftrace ops and dynamic trampolines - Allow stack traces to be passed from beginning event to end event for synthetic events. This will allow seeing the stack trace of when a task is scheduled out and recorded when it gets scheduled back in. - Add trace event helper __get_buf() to use as a temporary buffer when printing out trace event output. - Add kernel command line to create trace instances on boot up. - Add enabling of events to instances created at boot up. - Add trace_array_puts() to write into instances. - Allow boot instances to take a snapshot at the end of boot up. - Allow live patch modules to include trace events - Minor fixes and clean ups -----BEGIN PGP SIGNATURE----- iIoEABYIADIWIQRRSw7ePDh/lE+zeZMp5XQQmuv6qgUCY/PaaBQccm9zdGVkdEBn b29kbWlzLm9yZwAKCRAp5XQQmuv6qh5iAPoD0LKZzD33rhO5Ec4hoexE0DkqycP3 dvmOMbCBL8GkxwEA+d2gLz/EquSFm166hc4D79Sn3geCqvkwmy8vQWVjIQc= =M82D -----END PGP SIGNATURE----- Merge tag 'trace-v6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing updates from Steven Rostedt: - Add function names as a way to filter function addresses - Add sample module to test ftrace ops and dynamic trampolines - Allow stack traces to be passed from beginning event to end event for synthetic events. This will allow seeing the stack trace of when a task is scheduled out and recorded when it gets scheduled back in. - Add trace event helper __get_buf() to use as a temporary buffer when printing out trace event output. - Add kernel command line to create trace instances on boot up. - Add enabling of events to instances created at boot up. - Add trace_array_puts() to write into instances. - Allow boot instances to take a snapshot at the end of boot up. - Allow live patch modules to include trace events - Minor fixes and clean ups * tag 'trace-v6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (31 commits) tracing: Remove unnecessary NULL assignment tracepoint: Allow livepatch module add trace event tracing: Always use canonical ftrace path tracing/histogram: Fix stacktrace histogram Documententation tracing/histogram: Fix stacktrace key tracing/histogram: Fix a few problems with stacktrace variable printing tracing: Add BUILD_BUG() to make sure stacktrace fits in strings tracing/histogram: Don't use strlen to find length of stacktrace variables tracing: Allow boot instances to have snapshot buffers tracing: Add trace_array_puts() to write into instance tracing: Add enabling of events to boot instances tracing: Add creation of instances at boot command line tracing: Fix trace_event_raw_event_synth() if else statement samples: ftrace: Make some global variables static ftrace: sample: avoid open-coded 64-bit division samples: ftrace: Include the nospec-branch.h only for x86 tracing: Acquire buffer from temparary trace sequence tracing/histogram: Wrap remaining shell snippets in code blocks tracing/osnoise: No need for schedule_hrtimeout range bpf/tracing: Use stage6 of tracing to not duplicate macros ... |
||
|
Ross Zwisler
|
2455f0e124 |
tracing: Always use canonical ftrace path
The canonical location for the tracefs filesystem is at /sys/kernel/tracing. But, from Documentation/trace/ftrace.rst: Before 4.1, all ftrace tracing control files were within the debugfs file system, which is typically located at /sys/kernel/debug/tracing. For backward compatibility, when mounting the debugfs file system, the tracefs file system will be automatically mounted at: /sys/kernel/debug/tracing Many comments and Kconfig help messages in the tracing code still refer to this older debugfs path, so let's update them to avoid confusion. Link: https://lore.kernel.org/linux-trace-kernel/20230215223350.2658616-2-zwisler@google.com Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Reviewed-by: Mukesh Ojha <quic_mojha@quicinc.com> Signed-off-by: Ross Zwisler <zwisler@google.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Mukesh Ojha
|
8843e06f67 |
ring-buffer: Handle race between rb_move_tail and rb_check_pages
It seems a data race between ring_buffer writing and integrity check.
That is, RB_FLAG of head_page is been updating, while at same time
RB_FLAG was cleared when doing integrity check rb_check_pages():
rb_check_pages() rb_handle_head_page():
-------- --------
rb_head_page_deactivate()
rb_head_page_set_normal()
rb_head_page_activate()
We do intergrity test of the list to check if the list is corrupted and
it is still worth doing it. So, let's refactor rb_check_pages() such that
we no longer clear and set flag during the list sanity checking.
[1] and [2] are the test to reproduce and the crash report respectively.
1:
``` read_trace.sh
while true;
do
# the "trace" file is closed after read
head -1 /sys/kernel/tracing/trace > /dev/null
done
```
``` repro.sh
sysctl -w kernel.panic_on_warn=1
# function tracer will writing enough data into ring_buffer
echo function > /sys/kernel/tracing/current_tracer
./read_trace.sh &
./read_trace.sh &
./read_trace.sh &
./read_trace.sh &
./read_trace.sh &
./read_trace.sh &
./read_trace.sh &
./read_trace.sh &
```
2:
------------[ cut here ]------------
WARNING: CPU: 9 PID: 62 at kernel/trace/ring_buffer.c:2653
rb_move_tail+0x450/0x470
Modules linked in:
CPU: 9 PID: 62 Comm: ksoftirqd/9 Tainted: G W 6.2.0-rc6+
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014
RIP: 0010:rb_move_tail+0x450/0x470
Code: ff ff 4c 89 c8 f0 4d 0f b1 02 48 89 c2 48 83 e2 fc 49 39 d0 75 24
83 e0 03 83 f8 02 0f 84 e1 fb ff ff 48 8b 57 10 f0 ff 42 08 <0f> 0b 83
f8 02 0f 84 ce fb ff ff e9 db
RSP: 0018:ffffb5564089bd00 EFLAGS: 00000203
RAX: 0000000000000000 RBX: ffff9db385a2bf81 RCX: ffffb5564089bd18
RDX: ffff9db281110100 RSI: 0000000000000fe4 RDI: ffff9db380145400
RBP: ffff9db385a2bf80 R08: ffff9db385a2bfc0 R09: ffff9db385a2bfc2
R10: ffff9db385a6c000 R11: ffff9db385a2bf80 R12: 0000000000000000
R13: 00000000000003e8 R14: ffff9db281110100 R15: ffffffffbb006108
FS: 0000000000000000(0000) GS:ffff9db3bdcc0000(0000)
knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005602323024c8 CR3: 0000000022e0c000 CR4: 00000000000006e0
Call Trace:
<TASK>
ring_buffer_lock_reserve+0x136/0x360
? __do_softirq+0x287/0x2df
? __pfx_rcu_softirq_qs+0x10/0x10
trace_function+0x21/0x110
? __pfx_rcu_softirq_qs+0x10/0x10
? __do_softirq+0x287/0x2df
function_trace_call+0xf6/0x120
0xffffffffc038f097
? rcu_softirq_qs+0x5/0x140
rcu_softirq_qs+0x5/0x140
__do_softirq+0x287/0x2df
run_ksoftirqd+0x2a/0x30
smpboot_thread_fn+0x188/0x220
? __pfx_smpboot_thread_fn+0x10/0x10
kthread+0xe7/0x110
? __pfx_kthread+0x10/0x10
ret_from_fork+0x2c/0x50
</TASK>
---[ end trace 0000000000000000 ]---
[ crash report and test reproducer credit goes to Zheng Yejian]
Link: https://lore.kernel.org/linux-trace-kernel/1676376403-16462-1-git-send-email-quic_mojha@quicinc.com
Cc: <mhiramat@kernel.org>
Cc: stable@vger.kernel.org
Fixes:
|
||
|
Jia-Ju Bai
|
3e4272b995 |
tracing: Add NULL checks for buffer in ring_buffer_free_read_page()
In a previous commit
|
||
|
Steven Rostedt
|
88ca6a71dc |
ring-buffer: Handle resize in early boot up
With the new command line option that allows trace event triggers to be
added at boot, the "snapshot" trigger will allocate the snapshot buffer
very early, when interrupts can not be enabled. Allocating the ring buffer
is not the problem, but it also resizes it, which is, as the resize code
does synchronization that can not be preformed at early boot.
To handle this, first change the raw_spin_lock_irq() in rb_insert_pages()
to raw_spin_lock_irqsave(), such that the unlocking of that spin lock will
not enable interrupts.
Next, where it calls schedule_work_on(), disable migration and check if
the CPU to update is the current CPU, and if so, perform the work
directly, otherwise re-enable migration and call the schedule_work_on() to
the CPU that is being updated. The rb_insert_pages() just needs to be run
on the CPU that it is updating, and does not need preemption nor
interrupts disabled when calling it.
Link: https://lore.kernel.org/lkml/Y5J%2FCajlNh1gexvo@google.com/
Link: https://lore.kernel.org/linux-trace-kernel/20221209101151.1fec1167@gandalf.local.home
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes:
|
||
|
Song Chen
|
04aabc32fb |
ring_buffer: Remove unused "event" parameter
After commit
|
||
|
Daniil Tatianin
|
56f4ca0a79 |
ring_buffer: Do not deactivate non-existant pages
rb_head_page_deactivate() expects cpu_buffer to contain a valid list of
->pages, so verify that the list is actually present before calling it.
Found by Linux Verification Center (linuxtesting.org) with the SVACE
static analysis tool.
Link: https://lkml.kernel.org/r/20221114143129.3534443-1-d-tatianin@yandex-team.ru
Cc: stable@vger.kernel.org
Fixes:
|
||
|
Steven Rostedt (Google)
|
31029a8b2c |
ring-buffer: Include dropped pages in counting dirty patches
The function ring_buffer_nr_dirty_pages() was created to find out how many
pages are filled in the ring buffer. There's two running counters. One is
incremented whenever a new page is touched (pages_touched) and the other
is whenever a page is read (pages_read). The dirty count is the number
touched minus the number read. This is used to determine if a blocked task
should be woken up if the percentage of the ring buffer it is waiting for
is hit.
The problem is that it does not take into account dropped pages (when the
new writes overwrite pages that were not read). And then the dirty pages
will always be greater than the percentage.
This makes the "buffer_percent" file inaccurate, as the number of dirty
pages end up always being larger than the percentage, event when it's not
and this causes user space to be woken up more than it wants to be.
Add a new counter to keep track of lost pages, and include that in the
accounting of dirty pages so that it is actually accurate.
Link: https://lkml.kernel.org/r/20221021123013.55fb6055@gandalf.local.home
Fixes:
|
||
|
Steven Rostedt (Google)
|
42fb0a1e84 |
tracing/ring-buffer: Have polling block on watermark
Currently the way polling works on the ring buffer is broken. It will
return immediately if there's any data in the ring buffer whereas a read
will block until the watermark (defined by the tracefs buffer_percent file)
is hit.
That is, a select() or poll() will return as if there's data available,
but then the following read will block. This is broken for the way
select()s and poll()s are supposed to work.
Have the polling on the ring buffer also block the same way reads and
splice does on the ring buffer.
Link: https://lkml.kernel.org/r/20221020231427.41be3f26@gandalf.local.home
Cc: Linux Trace Kernel <linux-trace-kernel@vger.kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Primiano Tucci <primiano@google.com>
Cc: stable@vger.kernel.org
Fixes:
|
||
|
Steven Rostedt (Google)
|
7433632c9f |
ring-buffer: Check for NULL cpu_buffer in ring_buffer_wake_waiters()
On some machines the number of listed CPUs may be bigger than the actual
CPUs that exist. The tracing subsystem allocates a per_cpu directory with
access to the per CPU ring buffer via a cpuX file. But to save space, the
ring buffer will only allocate buffers for online CPUs, even though the
CPU array will be as big as the nr_cpu_ids.
With the addition of waking waiters on the ring buffer when closing the
file, the ring_buffer_wake_waiters() now needs to make sure that the
buffer is allocated (with the irq_work allocated with it) before trying to
wake waiters, as it will cause a NULL pointer dereference.
While debugging this, I added a NULL check for the buffer itself (which is
OK to do), and also NULL pointer checks against buffer->buffers (which is
not fine, and will WARN) as well as making sure the CPU number passed in
is within the nr_cpu_ids (which is also not fine if it isn't).
Link: https://lore.kernel.org/all/87h6zklb6n.wl-tiwai@suse.de/
Link: https://lore.kernel.org/all/CAM6Wdxc0KRJMXVAA0Y=u6Jh2V=uWB-_Fn6M4xRuNppfXzL1mUg@mail.gmail.com/
Link: https://lkml.kernel.org/linux-trace-kernel/20221101191009.1e7378c8@rorschach.local.home
Cc: stable@vger.kernel.org
Cc: Steven Noonan <steven.noonan@gmail.com>
Bugzilla: https://bugzilla.opensuse.org/show_bug.cgi?id=1204705
Reported-by: Takashi Iwai <tiwai@suse.de>
Reported-by: Roland Ruckerbauer <roland.rucky@gmail.com>
Fixes:
|
||
|
Jiapeng Chong
|
b7085b6ffe |
ring-buffer: Fix kernel-doc
kernel/trace/ring_buffer.c:895: warning: expecting prototype for ring_buffer_nr_pages_dirty(). Prototype was for ring_buffer_nr_dirty_pages() instead. kernel/trace/ring_buffer.c:5313: warning: expecting prototype for ring_buffer_reset_cpu(). Prototype was for ring_buffer_reset_online_cpus() instead. kernel/trace/ring_buffer.c:5382: warning: expecting prototype for rind_buffer_empty(). Prototype was for ring_buffer_empty() instead. Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=2340 Link: https://lkml.kernel.org/r/20221009020642.12506-1-jiapeng.chong@linux.alibaba.com Reported-by: Abaci Robot <abaci@linux.alibaba.com> Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
||
|
Steven Rostedt (Google)
|
a0fcaaed0c |
ring-buffer: Fix race between reset page and reading page
The ring buffer is broken up into sub buffers (currently of page size).
Each sub buffer has a pointer to its "tail" (the last event written to the
sub buffer). When a new event is requested, the tail is locally
incremented to cover the size of the new event. This is done in a way that
there is no need for locking.
If the tail goes past the end of the sub buffer, the process of moving to
the next sub buffer takes place. After setting the current sub buffer to
the next one, the previous one that had the tail go passed the end of the
sub buffer needs to be reset back to the original tail location (before
the new event was requested) and the rest of the sub buffer needs to be
"padded".
The race happens when a reader takes control of the sub buffer. As readers
do a "swap" of sub buffers from the ring buffer to get exclusive access to
the sub buffer, it replaces the "head" sub buffer with an empty sub buffer
that goes back into the writable portion of the ring buffer. This swap can
happen as soon as the writer moves to the next sub buffer and before it
updates the last sub buffer with padding.
Because the sub buffer can be released to the reader while the writer is
still updating the padding, it is possible for the reader to see the event
that goes past the end of the sub buffer. This can cause obvious issues.
To fix this, add a few memory barriers so that the reader definitely sees
the updates to the sub buffer, and also waits until the writer has put
back the "tail" of the sub buffer back to the last event that was written
on it.
To be paranoid, it will only spin for 1 second, otherwise it will
warn and shutdown the ring buffer code. 1 second should be enough as
the writer does have preemption disabled. If the writer doesn't move
within 1 second (with preemption disabled) something is horribly
wrong. No interrupt should last 1 second!
Link: https://lore.kernel.org/all/20220830120854.7545-1-jiazi.li@transsion.com/
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216369
Link: https://lkml.kernel.org/r/20220929104909.0650a36c@gandalf.local.home
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: stable@vger.kernel.org
Fixes:
|
||
|
Steven Rostedt (Google)
|
7e9fbbb1b7 |
ring-buffer: Add ring_buffer_wake_waiters()
On closing of a file that represents a ring buffer or flushing the file,
there may be waiters on the ring buffer that needs to be woken up and exit
the ring_buffer_wait() function.
Add ring_buffer_wake_waiters() to wake up the waiters on the ring buffer
and allow them to exit the wait loop.
Link: https://lkml.kernel.org/r/20220928133938.28dc2c27@gandalf.local.home
Cc: stable@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes:
|
||
|
Steven Rostedt (Google)
|
ec0bbc5ec5 |
ring-buffer: Check pending waiters when doing wake ups as well
The wake up waiters only checks the "wakeup_full" variable and not the
"full_waiters_pending". The full_waiters_pending is set when a waiter is
added to the wait queue. The wakeup_full is only set when an event is
triggered, and it clears the full_waiters_pending to avoid multiple calls
to irq_work_queue().
The irq_work callback really needs to check both wakeup_full as well as
full_waiters_pending such that this code can be used to wake up waiters
when a file is closed that represents the ring buffer and the waiters need
to be woken up.
Link: https://lkml.kernel.org/r/20220927231824.209460321@goodmis.org
Cc: stable@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes:
|
||
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Steven Rostedt (Google)
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3b19d614b6 |
ring-buffer: Have the shortest_full queue be the shortest not longest
The logic to know when the shortest waiters on the ring buffer should be
woken up or not has uses a less than instead of a greater than compare,
which causes the shortest_full to actually be the longest.
Link: https://lkml.kernel.org/r/20220927231823.718039222@goodmis.org
Cc: stable@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes:
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Steven Rostedt (Google)
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fa8f4a8973 |
ring-buffer: Allow splice to read previous partially read pages
If a page is partially read, and then the splice system call is run
against the ring buffer, it will always fail to read, no matter how much
is in the ring buffer. That's because the code path for a partial read of
the page does will fail if the "full" flag is set.
The splice system call wants full pages, so if the read of the ring buffer
is not yet full, it should return zero, and the splice will block. But if
a previous read was done, where the beginning has been consumed, it should
still be given to the splice caller if the rest of the page has been
written to.
This caused the splice command to never consume data in this scenario, and
let the ring buffer just fill up and lose events.
Link: https://lkml.kernel.org/r/20220927144317.46be6b80@gandalf.local.home
Cc: stable@vger.kernel.org
Fixes:
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Steven Rostedt (Google)
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f03f2abce4 |
ring-buffer: Have 32 bit time stamps use all 64 bits
When the new logic was made to handle deltas of events from interrupts
that interrupted other events, it required 64 bit local atomics.
Unfortunately, 64 bit local atomics are expensive on 32 bit architectures.
Thus, commit
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