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Commit 88f1c87d authored by Tejun Heo's avatar Tejun Heo Committed by Ingo Molnar
Browse files

locking/lockdep: Avoid triggering hardlockup from debug_show_all_locks() 



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: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
parent a97cb0e7

kernel/locking/lockdep.c

+2 −0
Original line number Diff line number Diff line
@@ -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 @@ void debug_show_all_locks(void) 
		if (!unlock)

			if (read_trylock(&tasklist_lock))

				unlock = 1;

		touch_nmi_watchdog();

	} while_each_thread(g, p);



	pr_warn("\n");