watchdog: fix barriers when printing backtraces from all CPUs
authorPetr Mladek <pmladek@suse.com>
Fri, 30 Apr 2021 05:54:33 +0000 (22:54 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Fri, 30 Apr 2021 18:20:36 +0000 (11:20 -0700)
commit9f113bf760ca90d709f8f89a733d10abb1f04a83
treec438c29ec307cfa2157de91f30a04643fc947259
parent1bc503cb4a2638fb1c57801a7796aca57845ce63
watchdog: fix barriers when printing backtraces from all CPUs

Any parallel softlockup reports are skipped when one CPU is already
printing backtraces from all CPUs.

The exclusive rights are synchronized using one bit in
soft_lockup_nmi_warn.  There is also one memory barrier that does not make
much sense.

Use two barriers on the right location to prevent mixing two reports.

[pmladek@suse.com: use bit lock operations to prevent multiple soft-lockup reports]
Link: https://lkml.kernel.org/r/YFSVsLGVWMXTvlbk@alley
Link: https://lkml.kernel.org/r/20210311122130.6788-6-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Laurence Oberman <loberman@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincent Whitchurch <vincent.whitchurch@axis.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
kernel/watchdog.c