[PATCH v6 17/46] clockevents: Use get/put_online_cpus_atomic() inclockevents_notify()

From: Srivatsa S. Bhat
Date: Mon Feb 18 2013 - 07:42:55 EST

The cpu idle code invokes clockevents_notify() during idle state transitions
and the cpu offline code invokes it during the CPU_DYING phase. There
seems to be a race-condition between the two, where the clockevents_lock
never gets released, ending in a lockup. This can be fixed by synchronizing
clockevents_notify() with CPU offline, by wrapping its contents within

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>

kernel/time/clockevents.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 30b6de0..ca340fd 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -17,6 +17,7 @@
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/smp.h>
+#include <linux/cpu.h>

#include "tick-internal.h"

@@ -431,6 +432,7 @@ void clockevents_notify(unsigned long reason, void *arg)
unsigned long flags;
int cpu;

+ get_online_cpus_atomic();
raw_spin_lock_irqsave(&clockevents_lock, flags);
clockevents_do_notify(reason, arg);

@@ -459,6 +461,7 @@ void clockevents_notify(unsigned long reason, void *arg)
raw_spin_unlock_irqrestore(&clockevents_lock, flags);
+ put_online_cpus_atomic();

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