linux-stable/Documentation/admin-guide/clearing-warn-once.rst

Clearing WARN_ONCE
------------------

WARN_ONCE / WARN_ON_ONCE / printk_once only emit a message once.

echo 1 > /sys/kernel/debug/clear_warn_once

clears the state and allows the warnings to print once again.
This can be useful after test suite runs to reproduce problems.
docs: clearing-warn-once.txt: add a title for this document This document misses a title. Add it, in order to follow the documentation standard. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net> 2019-04-10 09:56:22 +00:00			`Clearing WARN_ONCE`
			`------------------`
kernel debug: support resetting WARN*_ONCE I like _ONCE warnings because it's guaranteed that they don't flood the log. During testing I find it useful to reset the state of the once warnings, so that I can rerun tests and see if they trigger again, or can guarantee that a test run always hits the same warnings. This patch adds a debugfs interface to reset all the _ONCE warnings so that they appear again: echo 1 > /sys/kernel/debug/clear_warn_once This is implemented by putting all the warning booleans into a special section, and clearing it. [akpm@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/20171017221455.6740-1-andi@firstfloor.org Signed-off-by: Andi Kleen <ak@linux.intel.com> Tested-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 2017-11-17 23:27:03 +00:00
printk: Tie printk_once / printk_deferred_once into .data.once for reset In commit b1fca27d384e ("kernel debug: support resetting WARN_ONCE") we got the opportunity to reset state on the one shot messages, without having to reboot. However printk_once (printk_deferred_once) live in a different file and didn't get the same kind of update/conversion, so they remain unconditionally one shot, until the system is rebooted. For example, we currently have: sched/rt.c: printk_deferred_once("sched: RT throttling activated\n"); ..which could reasonably be tripped as someone is testing and tuning a new system/workload and their task placements. For consistency, and to avoid reboots in the same vein as the original commit, we make these two instances of _once the same as the WARN_ONCE instances are. Link: http://lkml.kernel.org/r/1555121491-31213-1-git-send-email-paul.gortmaker@windriver.com Cc: Andi Kleen <ak@linux.intel.com> Cc: Petr Mladek <pmladek@suse.com> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Petr Mladek <pmladek@suse.com> 2019-04-13 02:11:31 +00:00			`WARN_ONCE / WARN_ON_ONCE / printk_once only emit a message once.`
kernel debug: support resetting WARN*_ONCE I like _ONCE warnings because it's guaranteed that they don't flood the log. During testing I find it useful to reset the state of the once warnings, so that I can rerun tests and see if they trigger again, or can guarantee that a test run always hits the same warnings. This patch adds a debugfs interface to reset all the _ONCE warnings so that they appear again: echo 1 > /sys/kernel/debug/clear_warn_once This is implemented by putting all the warning booleans into a special section, and clearing it. [akpm@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/20171017221455.6740-1-andi@firstfloor.org Signed-off-by: Andi Kleen <ak@linux.intel.com> Tested-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 2017-11-17 23:27:03 +00:00
			`echo 1 > /sys/kernel/debug/clear_warn_once`

			`clears the state and allows the warnings to print once again.`
			`This can be useful after test suite runs to reproduce problems.`