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Mathieu Desnoyers 98bf0fbb65 tracing: Remove conditional locking from __DO_TRACE() 
Remove conditional locking by moving the __DO_TRACE() code into
trace_##name().

When the faultable syscall tracepoints were implemented, __DO_TRACE()
had a rcuidle argument which selected between SRCU and preempt disable.
Therefore, the RCU tasks trace protection for faultable syscall
tracepoints was introduced using the same pattern.

At that point, it did not appear obvious that this feedback from Linus [1]
applied here as well, because the __DO_TRACE() modification was
extending a pre-existing pattern.

Shortly before pulling the faultable syscall tracepoints modifications,
Steven removed the rcuidle argument and SRCU protection scheme entirely
from tracepoint.h:

commit 48bcda6848 ("tracing: Remove definition of trace_*_rcuidle()")

This required a rebase of the faultable syscall tracepoints series,
which missed a perfect opportunity to integrate the prior recommendation
from Linus.

In response to the pull request, Linus pointed out [2] that he was not
pleased by the implementation, expecting this to be fixed in a follow up
patch series.

Move __DO_TRACE() code into trace_##name() within each of
__DECLARE_TRACE() and __DECLARE_TRACE_SYSCALL(). Use a scoped guard
to guard the preempt disable notrace and RCU tasks trace critical
sections.

Link: https://lore.kernel.org/all/CAHk-=wggDLDeTKbhb5hh--x=-DQd69v41137M72m6NOTmbD-cw@mail.gmail.com/ [1]
Link: https://lore.kernel.org/lkml/CAHk-=witPrLcu22dZ93VCyRQonS7+-dFYhQbna=KBa-TAhayMw@mail.gmail.com/ [2]

Fixes: a363d27cdb ("tracing: Allow system call tracepoints to handle page faults")
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Michael Jeanson <mjeanson@efficios.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Yonghong Song <yhs@fb.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: bpf@vger.kernel.org
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Jordan Rife <jrife@google.com>
Cc: linux-trace-kernel@vger.kernel.org
Link: https://lore.kernel.org/20241123153031.2884933-5-mathieu.desnoyers@efficios.com
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
History 2024-11-23 17:49:23 -05:00
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README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.