Commit 177c53d9 authored Feb 28, 2014 by Peter Zijlstra Committed by Ingo Molnar Mar 11, 2014

stop_machine: Fix^2 race between stop_two_cpus() and stop_cpus()



We must use smp_call_function_single(.wait=1) for the
irq_cpu_stop_queue_work() to ensure the queueing is actually done under
stop_cpus_lock. Without this we could have dropped the lock by the time
we do the queueing and get the race we tried to fix.

Fixes: 7053ea1a ("stop_machine: Fix race between stop_two_cpus() and stop_cpus()")

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140228123905.GK3104@twins.programming.kicks-ass.net


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

parent d44753b8

kernel/stop_machine.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -293,7 +293,7 @@ int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *
		*/
		smp_call_function_single(min(cpu1, cpu2),
		&irq_cpu_stop_queue_work,
		&call_args, 0);
		&call_args, 1);
		lg_local_unlock(&stop_cpus_lock);
		preempt_enable();

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