From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
This patch does NOT apply to the 3.12 stable tree. If you still want
it applied, please provide a backport.
===============
commit 177c53d943368fc97644ebc0a250dc8e2d124250 upstream.
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: 7053ea1a34fa ("stop_machine: Fix race between stop_two_cpus() and stop_cpus()")
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Prarit Bhargava <prarit@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20140228123905.GK3104@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/stop_machine.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 84571e09c907..01fbae5b97b7 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -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();
--
1.9.1
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