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Thomas Richter ba5f102eec perf ftrace: Use process/session specific trace settings
Executing 'perf ftrace' commands 'ftrace', 'profile' and 'latency' leave
tracing disabled as can seen in this output:

 # echo 1 > /sys/kernel/debug/tracing/tracing_on
 # cat /sys/kernel/debug/tracing/tracing_on
 1
 # perf ftrace trace --graph-opts depth=5 sleep 0.1 > /dev/null
 # cat /sys/kernel/debug/tracing/tracing_on
 0
 #

The 'tracing_on' file is not restored to its value before the command.

To fix that this patch uses the .../tracing/instances/XXX subdirectory
feature.

Each 'perf ftrace' invocation creates its own session/process
specific subdirectory and does not change the global state
in the .../tracing directory itself.

Use rmdir(../tracing/instances/dir) to stop process/session specific
tracing and delete all process/session specific setings.

Reported-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Suggested-by: Arnaldo Carvalho de Melo <acme@kernel.org>
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Sumanth Korikkar <sumanthk@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Link: https://lore.kernel.org/r/20250520093726.2009696-1-tmricht@linux.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
History 2025-05-20 13:11:09 -03:00
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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.