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

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

Orabug: 25308017

[ Upstream commit 57675cb976eff977aefb428e68e4e0236d48a9ff ]

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>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
(cherry picked from commit 9f67dcf663004c56aaf153835f624f9f87d9a643)
Signed-off-by: Dhaval Giani <dhaval.giani@oracle.com>