Commit Graph

32 Commits

Author SHA1 Message Date
Paul E. McKenney
ba575cea29 ratelimit: Drop redundant accesses to burst
Now that there is the "burst <= 0" fastpath, for all later code, burst
must be strictly greater than zero.  Therefore, drop the redundant checks
of this local variable.

Link: https://lore.kernel.org/all/fbe93a52-365e-47fe-93a4-44a44547d601@paulmck-laptop/
Link: https://lore.kernel.org/all/20250423115409.3425-1-spasswolf@web.de/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
2025-05-08 16:13:27 -07:00
Paul E. McKenney
4b2cce999c ratelimit: Use nolock_ret restructuring to collapse common case code
Now that unlock_ret releases the lock, then falls into nolock_ret, which
handles ->missed based on the value of ret, the common-case lock-held
code can be collapsed into a single "if" statement with a single-statement
"then" clause.

Yes, we could go further and just assign the "if" condition to ret,
but in the immortal words of MSDOS, "Are you sure?".

Link: https://lore.kernel.org/all/fbe93a52-365e-47fe-93a4-44a44547d601@paulmck-laptop/
Link: https://lore.kernel.org/all/20250423115409.3425-1-spasswolf@web.de/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
2025-05-08 16:13:27 -07:00
Paul E. McKenney
743a1942d5 ratelimit: Use nolock_ret label to collapse lock-failure code
Now that we have a nolock_ret label that handles ->missed correctly
based on the value of ret, we can eliminate a local variable and collapse
several "if" statements on the lock-acquisition-failure code path.

Link: https://lore.kernel.org/all/fbe93a52-365e-47fe-93a4-44a44547d601@paulmck-laptop/
Link: https://lore.kernel.org/all/20250423115409.3425-1-spasswolf@web.de/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
2025-05-08 16:13:27 -07:00
Paul E. McKenney
a69114c2a1 ratelimit: Use nolock_ret label to save a couple of lines of code
Create a nolock_ret label in order to start consolidating the unlocked
return paths that conditionally invoke ratelimit_state_inc_miss().

Link: https://lore.kernel.org/all/fbe93a52-365e-47fe-93a4-44a44547d601@paulmck-laptop/
Link: https://lore.kernel.org/all/20250423115409.3425-1-spasswolf@web.de/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
2025-05-08 16:13:27 -07:00
Paul E. McKenney
f2d0ea0f08 ratelimit: Simplify common-case exit path
By making "ret" always be initialized, and moving the final call to
ratelimit_state_inc_miss() out from under the lock, we save a goto and
a couple lines of code.  This also saves a couple of lines of code from
the unconditional enable/disable slowpath.

Link: https://lore.kernel.org/all/fbe93a52-365e-47fe-93a4-44a44547d601@paulmck-laptop/
Link: https://lore.kernel.org/all/20250423115409.3425-1-spasswolf@web.de/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
2025-05-08 16:13:27 -07:00
Petr Mladek
a940d145cc ratelimit: Warn if ->interval or ->burst are negative
Currently, ___ratelimit() treats a negative ->interval or ->burst as
if it was zero, but this is an accident of the current implementation.
Therefore, splat in this case, which might have the benefit of detecting
use of uninitialized ratelimit_state structures on the one hand or easing
addition of new features on the other.

Link: https://lore.kernel.org/all/fbe93a52-365e-47fe-93a4-44a44547d601@paulmck-laptop/
Link: https://lore.kernel.org/all/20250423115409.3425-1-spasswolf@web.de/
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
2025-05-08 16:13:27 -07:00
Paul E. McKenney
96d366048f ratelimit: Avoid atomic decrement under lock if already rate-limited
Currently, if the lock is acquired, the code unconditionally does
an atomic decrement on ->rs_n_left, even if that atomic operation is
guaranteed to return a limit-rate verdict.  A limit-rate verdict will
in fact be the common case when something is spewing into a rate limit.
This unconditional atomic operation incurs needless overhead and also
raises the spectre of counter wrap.

Therefore, do the atomic decrement only if there is some chance that
rates won't be limited.

Link: https://lore.kernel.org/all/fbe93a52-365e-47fe-93a4-44a44547d601@paulmck-laptop/
Link: https://lore.kernel.org/all/20250423115409.3425-1-spasswolf@web.de/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
2025-05-08 16:13:27 -07:00
Paul E. McKenney
123a1d97b2 ratelimit: Avoid atomic decrement if already rate-limited
Currently, if the lock could not be acquired, the code unconditionally
does an atomic decrement on ->rs_n_left, even if that atomic operation
is guaranteed to return a limit-rate verdict.  This incurs needless
overhead and also raises the spectre of counter wrap.

Therefore, do the atomic decrement only if there is some chance that
rates won't be limited.

Link: https://lore.kernel.org/all/fbe93a52-365e-47fe-93a4-44a44547d601@paulmck-laptop/
Link: https://lore.kernel.org/all/20250423115409.3425-1-spasswolf@web.de/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
2025-05-08 16:13:27 -07:00
Paul E. McKenney
21ac6e5eda ratelimit: Don't flush misses counter if RATELIMIT_MSG_ON_RELEASE
Restore the previous semantics where the misses counter is unchanged if
the RATELIMIT_MSG_ON_RELEASE flag is set.

Link: https://lore.kernel.org/all/fbe93a52-365e-47fe-93a4-44a44547d601@paulmck-laptop/
Link: https://lore.kernel.org/all/20250423115409.3425-1-spasswolf@web.de/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
2025-05-08 16:13:27 -07:00
Paul E. McKenney
aa2cc356f8 ratelimit: Force re-initialization when rate-limiting re-enabled
Currently, if rate limiting is disabled, ___ratelimit() does an immediate
early return with no state changes.  This can result in false-positive
drops when re-enabling rate limiting.  Therefore, mark the ratelimit_state
structure "uninitialized" when rate limiting is disabled.

[ paulmck: Apply Petr Mladek feedback. ]

Link: https://lore.kernel.org/all/fbe93a52-365e-47fe-93a4-44a44547d601@paulmck-laptop/
Link: https://lore.kernel.org/all/20250423115409.3425-1-spasswolf@web.de/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
2025-05-08 16:13:27 -07:00
Paul E. McKenney
084a990ded ratelimit: Allow zero ->burst to disable ratelimiting
If ->interval is zero, then rate-limiting will be disabled.
Alternatively, if interval is greater than zero and ->burst is zero,
then rate-limiting will be applied unconditionally.  The point of this
distinction is to handle current users that pass zero-initialized
ratelimit_state structures to ___ratelimit(), and in such cases the
->lock field will be uninitialized.  Acquiring ->lock in this case is
clearly not a strategy to win.

Therefore, make this classification be lockless.

Note that although negative ->interval and ->burst happen to be treated
as if they were zero, this is an accident of the current implementation.
The semantics of negative values for these fields is subject to change
without notice.  Especially given that Bert Karwatzki determined that
no current calls to ___ratelimit() ever have negative values for these
fields.

This commit replaces an earlier buggy versions.

Link: https://lore.kernel.org/all/fbe93a52-365e-47fe-93a4-44a44547d601@paulmck-laptop/
Link: https://lore.kernel.org/all/20250423115409.3425-1-spasswolf@web.de/
Reported-by: Bert Karwatzki <spasswolf@web.de>
Reported-by: "Aithal, Srikanth" <sraithal@amd.com>
Closes: https://lore.kernel.org/all/20250423115409.3425-1-spasswolf@web.de/
Reported-by: Mark Brown <broonie@kernel.org>
Closes: https://lore.kernel.org/all/257c3b91-e30f-48be-9788-d27a4445a416@sirena.org.uk/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: "Aithal, Srikanth" <sraithal@amd.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
2025-05-08 16:13:27 -07:00
Petr Mladek
cf8cfa8a99 ratelimit: Reduce ___ratelimit() false-positive rate limiting
Retain the locked design, but check rate-limiting even when the lock
could not be acquired.

Link: https://lore.kernel.org/all/Z_VRo63o2UsVoxLG@pathway.suse.cz/
Link: https://lore.kernel.org/all/fbe93a52-365e-47fe-93a4-44a44547d601@paulmck-laptop/
Link: https://lore.kernel.org/all/20250423115409.3425-1-spasswolf@web.de/
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
2025-05-08 16:13:27 -07:00
Paul E. McKenney
e64a348dc1 ratelimit: Avoid jiffies=0 special case
The ___ratelimit() function special-cases the jiffies-counter value of zero
as "uninitialized".  This works well on 64-bit systems, where the jiffies
counter is not going to return to zero for more than half a billion years
on systems with HZ=1000, but similar 32-bit systems take less than 50 days
to wrap the jiffies counter.  And although the consequences of wrapping the
jiffies counter seem to be limited to minor confusion on the duration of
the rate-limiting interval that happens to end at time zero, it is almost
no work to avoid this confusion.

Therefore, introduce a RATELIMIT_INITIALIZED bit to the ratelimit_state
structure's ->flags field so that a ->begin value of zero is no longer
special.

Link: https://lore.kernel.org/all/fbe93a52-365e-47fe-93a4-44a44547d601@paulmck-laptop/
Link: https://lore.kernel.org/all/20250423115409.3425-1-spasswolf@web.de/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
2025-05-08 16:13:26 -07:00
Paul E. McKenney
d343732ddb ratelimit: Count misses due to lock contention
The ___ratelimit() function simply returns zero ("do ratelimiting")
if the trylock fails, but does not adjust the ->missed field.  This
means that the resulting dropped printk()s are dropped silently, which
could seriously confuse people trying to do console-log-based debugging.
Therefore, increment the ->missed field upon trylock failure.

Link: https://lore.kernel.org/all/fbe93a52-365e-47fe-93a4-44a44547d601@paulmck-laptop/
Link: https://lore.kernel.org/all/20250423115409.3425-1-spasswolf@web.de/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
2025-05-08 16:13:26 -07:00
Paul E. McKenney
78bf44de47 ratelimit: Convert the ->missed field to atomic_t
The ratelimit_state structure's ->missed field is sometimes incremented
locklessly, and it would be good to avoid lost counts.  This is also
needed to count the number of misses due to trylock failure.  Therefore,
convert the ratelimit_state structure's ->missed field to atomic_t.

Link: https://lore.kernel.org/all/fbe93a52-365e-47fe-93a4-44a44547d601@paulmck-laptop/
Link: https://lore.kernel.org/all/20250423115409.3425-1-spasswolf@web.de/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
2025-05-08 16:13:26 -07:00
Paul E. McKenney
56a7b9f8b0 ratelimit: Create functions to handle ratelimit_state internals
A number of ratelimit use cases do open-coded access to the
ratelimit_state structure's ->missed field.  This works, but is a bit
messy and makes it more annoying to make changes to this field.

Therefore, provide a ratelimit_state_inc_miss() function that increments
the ->missed field, a ratelimit_state_get_miss() function that reads
out the ->missed field, and a ratelimit_state_reset_miss() function
that reads out that field, but that also resets its value to zero.
These functions will replace client-code open-coded uses of ->missed.

In addition, a new ratelimit_state_reset_interval() function encapsulates
what was previously open-coded lock acquisition and direct field updates.

[ paulmck: Apply kernel test robot feedback. ]

Link: https://lore.kernel.org/all/fbe93a52-365e-47fe-93a4-44a44547d601@paulmck-laptop/
Link: https://lore.kernel.org/all/20250423115409.3425-1-spasswolf@web.de/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
2025-05-08 16:13:26 -07:00
Kuniyuki Iwashima
6bae8ceb90 ratelimit: Fix data-races in ___ratelimit().
While reading rs->interval and rs->burst, they can be changed
concurrently via sysctl (e.g. net_ratelimit_state).  Thus, we
need to add READ_ONCE() to their readers.

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2022-08-24 13:46:57 +01:00
Thomas Gleixner
55716d2643 treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 428
Based on 1 normalized pattern(s):

  this file is released under the gplv2

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-only

has been chosen to replace the boilerplate/reference in 68 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Armijn Hemel <armijn@tjaldur.nl>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190531190114.292346262@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-06-05 17:37:16 +02:00
Sergey Senozhatsky
656d61ce96 lib/ratelimit.c: use deferred printk() version
printk_ratelimit() invokes ___ratelimit() which may invoke a normal
printk() (pr_warn() in this particular case) to warn about suppressed
output.  Given that printk_ratelimit() may be called from anywhere, that
pr_warn() is dangerous - it may end up deadlocking the system.  Fix
___ratelimit() by using deferred printk().

Sasha reported the following lockdep error:

 : Unregister pv shared memory for cpu 8
 : select_fallback_rq: 3 callbacks suppressed
 : process 8583 (trinity-c78) no longer affine to cpu8
 :
 : ======================================================
 : WARNING: possible circular locking dependency detected
 : 4.14.0-rc2-next-20170927+ #252 Not tainted
 : ------------------------------------------------------
 : migration/8/62 is trying to acquire lock:
 : (&port_lock_key){-.-.}, at: serial8250_console_write()
 :
 : but task is already holding lock:
 : (&rq->lock){-.-.}, at: sched_cpu_dying()
 :
 : which lock already depends on the new lock.
 :
 :
 : the existing dependency chain (in reverse order) is:
 :
 : -> #3 (&rq->lock){-.-.}:
 : __lock_acquire()
 : lock_acquire()
 : _raw_spin_lock()
 : task_fork_fair()
 : sched_fork()
 : copy_process.part.31()
 : _do_fork()
 : kernel_thread()
 : rest_init()
 : start_kernel()
 : x86_64_start_reservations()
 : x86_64_start_kernel()
 : verify_cpu()
 :
 : -> #2 (&p->pi_lock){-.-.}:
 : __lock_acquire()
 : lock_acquire()
 : _raw_spin_lock_irqsave()
 : try_to_wake_up()
 : default_wake_function()
 : woken_wake_function()
 : __wake_up_common()
 : __wake_up_common_lock()
 : __wake_up()
 : tty_wakeup()
 : tty_port_default_wakeup()
 : tty_port_tty_wakeup()
 : uart_write_wakeup()
 : serial8250_tx_chars()
 : serial8250_handle_irq.part.25()
 : serial8250_default_handle_irq()
 : serial8250_interrupt()
 : __handle_irq_event_percpu()
 : handle_irq_event_percpu()
 : handle_irq_event()
 : handle_level_irq()
 : handle_irq()
 : do_IRQ()
 : ret_from_intr()
 : native_safe_halt()
 : default_idle()
 : arch_cpu_idle()
 : default_idle_call()
 : do_idle()
 : cpu_startup_entry()
 : rest_init()
 : start_kernel()
 : x86_64_start_reservations()
 : x86_64_start_kernel()
 : verify_cpu()
 :
 : -> #1 (&tty->write_wait){-.-.}:
 : __lock_acquire()
 : lock_acquire()
 : _raw_spin_lock_irqsave()
 : __wake_up_common_lock()
 : __wake_up()
 : tty_wakeup()
 : tty_port_default_wakeup()
 : tty_port_tty_wakeup()
 : uart_write_wakeup()
 : serial8250_tx_chars()
 : serial8250_handle_irq.part.25()
 : serial8250_default_handle_irq()
 : serial8250_interrupt()
 : __handle_irq_event_percpu()
 : handle_irq_event_percpu()
 : handle_irq_event()
 : handle_level_irq()
 : handle_irq()
 : do_IRQ()
 : ret_from_intr()
 : native_safe_halt()
 : default_idle()
 : arch_cpu_idle()
 : default_idle_call()
 : do_idle()
 : cpu_startup_entry()
 : rest_init()
 : start_kernel()
 : x86_64_start_reservations()
 : x86_64_start_kernel()
 : verify_cpu()
 :
 : -> #0 (&port_lock_key){-.-.}:
 : check_prev_add()
 : __lock_acquire()
 : lock_acquire()
 : _raw_spin_lock_irqsave()
 : serial8250_console_write()
 : univ8250_console_write()
 : console_unlock()
 : vprintk_emit()
 : vprintk_default()
 : vprintk_func()
 : printk()
 : ___ratelimit()
 : __printk_ratelimit()
 : select_fallback_rq()
 : sched_cpu_dying()
 : cpuhp_invoke_callback()
 : take_cpu_down()
 : multi_cpu_stop()
 : cpu_stopper_thread()
 : smpboot_thread_fn()
 : kthread()
 : ret_from_fork()
 :
 : other info that might help us debug this:
 :
 : Chain exists of:
 :   &port_lock_key --> &p->pi_lock --> &rq->lock
 :
 :  Possible unsafe locking scenario:
 :
 :        CPU0                    CPU1
 :        ----                    ----
 :   lock(&rq->lock);
 :                                lock(&p->pi_lock);
 :                                lock(&rq->lock);
 :   lock(&port_lock_key);
 :
 :  *** DEADLOCK ***
 :
 : 4 locks held by migration/8/62:
 : #0: (&p->pi_lock){-.-.}, at: sched_cpu_dying()
 : #1: (&rq->lock){-.-.}, at: sched_cpu_dying()
 : #2: (printk_ratelimit_state.lock){....}, at: ___ratelimit()
 : #3: (console_lock){+.+.}, at: vprintk_emit()
 :
 : stack backtrace:
 : CPU: 8 PID: 62 Comm: migration/8 Not tainted 4.14.0-rc2-next-20170927+ #252
 : Call Trace:
 : dump_stack()
 : print_circular_bug()
 : check_prev_add()
 : ? add_lock_to_list.isra.26()
 : ? check_usage()
 : ? kvm_clock_read()
 : ? kvm_sched_clock_read()
 : ? sched_clock()
 : ? check_preemption_disabled()
 : __lock_acquire()
 : ? __lock_acquire()
 : ? add_lock_to_list.isra.26()
 : ? debug_check_no_locks_freed()
 : ? memcpy()
 : lock_acquire()
 : ? serial8250_console_write()
 : _raw_spin_lock_irqsave()
 : ? serial8250_console_write()
 : serial8250_console_write()
 : ? serial8250_start_tx()
 : ? lock_acquire()
 : ? memcpy()
 : univ8250_console_write()
 : console_unlock()
 : ? __down_trylock_console_sem()
 : vprintk_emit()
 : vprintk_default()
 : vprintk_func()
 : printk()
 : ? show_regs_print_info()
 : ? lock_acquire()
 : ___ratelimit()
 : __printk_ratelimit()
 : select_fallback_rq()
 : sched_cpu_dying()
 : ? sched_cpu_starting()
 : ? rcutree_dying_cpu()
 : ? sched_cpu_starting()
 : cpuhp_invoke_callback()
 : ? cpu_disable_common()
 : take_cpu_down()
 : ? trace_hardirqs_off_caller()
 : ? cpuhp_invoke_callback()
 : multi_cpu_stop()
 : ? __this_cpu_preempt_check()
 : ? cpu_stop_queue_work()
 : cpu_stopper_thread()
 : ? cpu_stop_create()
 : smpboot_thread_fn()
 : ? sort_range()
 : ? schedule()
 : ? __kthread_parkme()
 : kthread()
 : ? sort_range()
 : ? kthread_create_on_node()
 : ret_from_fork()
 : process 9121 (trinity-c78) no longer affine to cpu8
 : smpboot: CPU 8 is now offline

Link: http://lkml.kernel.org/r/20170928120405.18273-1-sergey.senozhatsky@gmail.com
Fixes: 6b1d174b0c ("ratelimit: extend to print suppressed messages on release")
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reported-by: Sasha Levin <levinsasha928@gmail.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Borislav Petkov <bp@suse.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-10-03 17:54:26 -07:00
Borislav Petkov
6b1d174b0c ratelimit: extend to print suppressed messages on release
Extend the ratelimiting facility to print the amount of suppressed lines
when it is being released.

This use case is aimed at short-termed, burst-like users for which we
want to output the suppressed lines stats only once, after it has been
disposed of.  For an example, see /dev/kmsg usage in a follow-on patch.

Also, change the printk() line we issue on release to not use
"callbacks" as it is misleading: we're not suppressing callbacks but
printk() calls.

This has been separated from a previous patch by Linus.

Link: http://lkml.kernel.org/r/20160716061745.15795-2-bp@alien8.de
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Dave Young <dyoung@redhat.com>
Cc: Franck Bui <fbui@suse.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-08-02 19:35:06 -04:00
Jaewon Kim
c2594bc37f ratelimit: fix bug in time interval by resetting right begin time
rs->begin in ratelimit is set in two cases.
 1) when rs->begin was not initialized
 2) when rs->interval was passed

For case #2, current ratelimit sets the begin to 0.  This incurrs
improper suppression.  The begin value will be set in the next ratelimit
call by 1).  Then the time interval check will be always false, and
rs->printed will not be initialized.  Although enough time passed,
ratelimit may return 0 if rs->printed is not less than rs->burst.  To
reset interval properly, begin should be jiffies rather than 0.

For an example code below:

    static DEFINE_RATELIMIT_STATE(mylimit, 1, 1);
    for (i = 1; i <= 10; i++) {
        if (__ratelimit(&mylimit))
            printk("ratelimit test count %d\n", i);
        msleep(3000);
    }

test result in the current code shows suppression even there is 3 seconds sleep.

  [  78.391148] ratelimit test count 1
  [  81.295988] ratelimit test count 2
  [  87.315981] ratelimit test count 4
  [  93.336267] ratelimit test count 6
  [  99.356031] ratelimit test count 8
  [ 105.376367] ratelimit test count 10

Signed-off-by: Jaewon Kim <jaewon31.kim@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-01-21 17:20:51 -08:00
Paul Gortmaker
8bc3bcc93a lib: reduce the use of module.h wherever possible
For files only using THIS_MODULE and/or EXPORT_SYMBOL, map
them onto including export.h -- or if the file isn't even
using those, then just delete the include.  Fix up any implicit
include dependencies that were being masked by module.h along
the way.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2012-03-07 15:04:04 -05:00
Thomas Gleixner
07354eb1a7 locking, printk: Annotate logbuf_lock as raw
The logbuf_lock lock can be taken in atomic context and therefore
cannot be preempted on -rt - annotate it.

In mainline this change documents the low level nature of
the lock - otherwise there's no functional difference. Lockdep
and Sparse checking will work as usual.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[ merged and fixed it ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-09-13 11:11:54 +02:00
Yong Zhang
57119c34e5 ratelimit: fix the return value when __ratelimit() fails to acquire the lock
The log of commit edaac8e316 ("ratelimit:
Fix/allow use in atomic contexts"), indicates that we want to suppress the
callback when the trylock fails.

Signed-off-by: Yong Zhang <yong.zhang@windriver.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-04-07 08:38:04 -07:00
Yong Zhang
2a7268abc4 ratelimit: annotate ___ratelimit()
To prevent from wrongly using the return value.

[akpm@linux-foundation.org: fix spello]
Signed-off-by: Yong Zhang <yong.zhang@windriver.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Dave Young <hidave.darkstar@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-04-07 08:38:04 -07:00
Christian Borntraeger
5c82871335 ratelimit: Make suppressed output messages more useful
Today I got:

  [39648.224782] Registered led device: iwl-phy0::TX
  [40676.545099] __ratelimit: 246 callbacks suppressed
  [40676.545103] abcdef[23675]: segfault at 0 ...

as you can see the ratelimit message contains a function prefix.
Since this is always __ratelimit, this wont help much.

This patch changes __ratelimit and printk_ratelimit to print the
function name that calls ratelimit.

This will pinpoint the responsible function, as long as not several
different places call ratelimit with the same ratelimit state at
the same time. In that case we catch only one random function that
calls ratelimit after the wait period.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Dave Young <hidave.darkstar@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
CC: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <200910231458.11832.borntraeger@de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-10-23 17:26:37 +02:00
Ingo Molnar
3fff4c42bd printk: Remove ratelimit.h from kernel.h
Decouple kernel.h from ratelimit.h: the global declaration of
printk's ratelimit_state is not needed, and it leads to messy
circular dependencies due to ratelimit.h's (new) adding of a
spinlock_types.h include.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: David S. Miller <davem@davemloft.net>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-22 16:18:09 +02:00
Ingo Molnar
edaac8e316 ratelimit: Fix/allow use in atomic contexts
I'd like to use printk_ratelimit() in NMI context, but it's not
robust right now due to spinlock usage in lib/ratelimit.c. If an
NMI is unlucky enough to hit just that spot we might lock up trying
to take the spinlock again.

Fix that by using a trylock variant. If we contend on that lock we
can genuinely skip the message because the state is just being
accessed by another CPU (or by this CPU).

( We could use atomics for the suppressed messages field, but
  i doubt it matters in practice and it makes the code heavier. )

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: David S. Miller <davem@davemloft.net>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-22 14:05:48 +02:00
Ingo Molnar
979f693def ratelimit: Use per ratelimit context locking
I'd like to use printk_ratelimit() in atomic context, but that's
not possible right now due to the spinlock usage this commit
introduced more than a year ago:

  717115e: printk ratelimiting rewrite

As a first step push the lock into the ratelimit state structure.
This allows us to deal with locking failures to be considered as an
event related to that state being too busy.

Also clean up the code a bit (without changing functionality):

 - tidy up the definitions

 - clean up the code flow

This also shrinks the code a tiny bit:

   text	   data	    bss	    dec	    hex	filename
    264	      0	      4	    268	    10c	ratelimit.o.before
    255	      0	      0	    255	     ff	ratelimit.o.after

( Whole-kernel data size got a bit larger, because we have
  two ratelimit-state data structures right now. )

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: David S. Miller <davem@davemloft.net>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-22 15:31:34 +02:00
Alexey Dobriyan
4d9c377c81 __ratelimit() cpu flags can't be static
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Dave Young <hidave.darkstar@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-07-28 16:30:20 -07:00
Dave Young
717115e1a5 printk ratelimiting rewrite
All ratelimit user use same jiffies and burst params, so some messages
(callbacks) will be lost.

For example:
a call printk_ratelimit(5 * HZ, 1)
b call printk_ratelimit(5 * HZ, 1) before the 5*HZ timeout of a, then b will
will be supressed.

- rewrite __ratelimit, and use a ratelimit_state as parameter.  Thanks for
  hints from andrew.

- Add WARN_ON_RATELIMIT, update rcupreempt.h

- remove __printk_ratelimit

- use __ratelimit in net_ratelimit

Signed-off-by: Dave Young <hidave.darkstar@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Cc: Dave Young <hidave.darkstar@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-07-25 10:53:29 -07:00
Dave Young
5f97a5a879 isolate ratelimit from printk.c for other use
Due to the rcupreempt.h WARN_ON trigged, I got 2G syslog file.  For some
serious complaining of kernel, we need repeat the warnings, so here I isolate
the ratelimit part of printk.c to a standalone file.

Signed-off-by: Dave Young <hidave.darkstar@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-29 08:06:06 -07:00