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locking/lockdep: Avoid triggering hardlockup from debug_show_all_locks()

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debug_show_all_locks() iterates all tasks and print held locks whole
holding tasklist_lock.  This can take a while on a slow console device
and may end up triggering NMI hardlockup detector if someone else ends
up waiting for tasklist_lock.

Touch the NMI watchdog while printing the held locks to avoid
spuriously triggering the hardlockup detector.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kernel-team@fb.com
Link: http://lkml.kernel.org/r/20180122220055.GB1771050@devbig577.frc2.facebook.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Tejun Heo 2018-01-22 14:00:55 -08:00 committed by Ingo Molnar
parent a97cb0e7b3
commit 88f1c87de1
1 changed files with 2 additions and 0 deletions
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2
kernel/locking/lockdep.c
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@ -49,6 +49,7 @@
#include <linux/gfp.h>
#include <linux/random.h>
#include <linux/jhash.h>
#include <linux/nmi.h>
#include <asm/sections.h>
@ -4490,6 +4491,7 @@ retry:
if (!unlock)
if (read_trylock(&tasklist_lock))
unlock = 1;
touch_nmi_watchdog();
} while_each_thread(g, p);
pr_warn("\n");