Commit 57675cb9 authored Jun 09, 2016 by Andrey Ryabinin Committed by Ingo Molnar Jun 14, 2016

kernel/sysrq, watchdog, sched/core: Reset watchdog on all CPUs while processing sysrq-w



Lengthy output of sysrq-w may take a lot of time on slow serial console.

Currently we reset NMI-watchdog on the current CPU to avoid spurious
lockup messages. Sometimes this doesn't work since softlockup watchdog
might trigger on another CPU which is waiting for an IPI to proceed.
We reset softlockup watchdogs on all CPUs, but we do this only after
listing all tasks, and this may be too late on a busy system.

So, reset watchdogs CPUs earlier, in for_each_process_thread() loop.

Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/1465474805-14641-1-git-send-email-aryabinin@virtuozzo.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent eda8dca5

kernel/sched/core.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -5147,14 +5147,16 @@ void show_state_filter(unsigned long state_filter)
		/*
		* reset the NMI-timeout, listing all files on a slow
		* console might take a lot of time:
		* Also, reset softlockup watchdogs on all CPUs, because
		* another CPU might be blocked waiting for us to process
		* an IPI.
		*/
		touch_nmi_watchdog();
		touch_all_softlockup_watchdogs();
		if (!state_filter \|\| (p->state & state_filter))
		sched_show_task(p);
		}

		touch_all_softlockup_watchdogs();

		#ifdef CONFIG_SCHED_DEBUG
		if (!state_filter)
		sysrq_sched_debug_show();

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