linux/clearing-warn-once.txt at ba3c2b196bf59ba8574808fe6f8fd88d0fed7510 - linux - ClassFun

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Andi Kleen b1fca27d38 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 16:10:00 -08:00

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 WARN_ONCE / WARN_ON_ONCE only print a warning 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.