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In January 2015, tracefs was created to allow access to the tracing infrastructure without needing to compile in debugfs. When tracefs is configured, the directory /sys/kernel/tracing will exist and tooling is expected to use that path to access the tracing infrastructure. To allow backward compatibility, when debugfs is mounted, it would automount tracefs in its "tracing" directory so that tooling that had hard coded /sys/kernel/debug/tracing would still work. It has been over 10 years since the new interface was introduced, and all tooling should now be using it. Start the process of deprecating the old path so that it doesn't need to be maintained anymore. A new config is added to allow distributions to disable automounting of tracefs on debugfs. If /sys/kernel/debug/tracing is accessed, a pr_warn() will trigger stating: "NOTICE: Automounting of tracing to debugfs is deprecated and will be removed in 2030" Expect to remove this feature in 5 years (2030). Cc: <linux-trace-users@vger.kernel.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Christian Brauner <brauner@kernel.org> Cc: Jan Kara <jack@suse.cz> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Ian Rogers <irogers@google.com> Link: https://lore.kernel.org/20250722170806.40c068c6@gandalf.local.home Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
21 lines
894 B
Plaintext
21 lines
894 B
Plaintext
What: /sys/kernel/debug/tracing
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Date: May 2008
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KernelVersion: 2.6.27
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Contact: linux-trace-kernel@vger.kernel.org
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Description:
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The ftrace was first added to the kernel, its interface was placed
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into the debugfs file system under the "tracing" directory. Access
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to the files were in /sys/kernel/debug/tracing. As systems wanted
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access to the tracing interface without having to enable debugfs, a
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new interface was created called "tracefs". This was a stand alone
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file system and was usually mounted in /sys/kernel/tracing.
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To allow older tooling to continue to operate, when mounting
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debugfs, the tracefs file system would automatically get mounted in
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the "tracing" directory of debugfs. The tracefs interface was added
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in January 2015 in the v4.1 kernel.
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All tooling should now be using tracefs directly and the "tracing"
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directory in debugfs should be removed by January 2030.
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