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From: Yong Zhang <yong.zhang0@gmail.com>
Date: Thu, 28 Jul 2011 11:16:00 +0800
Subject: hotplug: Reread hotplug_pcp on pin_current_cpu() retry
When retry happens, it's likely that the task has been migrated to
another cpu (except unplug failed), but it still derefernces the
original hotplug_pcp per cpu data.
Update the pointer to hotplug_pcp in the retry path, so it points to
the current cpu.
Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110728031600.GA338@windriver.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/cpu.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
Index: linux-stable/kernel/cpu.c
===================================================================
--- linux-stable.orig/kernel/cpu.c
+++ linux-stable/kernel/cpu.c
@@ -81,9 +81,11 @@ static DEFINE_PER_CPU(struct hotplug_pcp
*/
void pin_current_cpu(void)
{
- struct hotplug_pcp *hp = &__get_cpu_var(hotplug_pcp);
+ struct hotplug_pcp *hp;
retry:
+ hp = &__get_cpu_var(hotplug_pcp);
+
if (!hp->unplug || hp->refcount || preempt_count() > 1 ||
hp->unplug == current || (current->flags & PF_STOMPER)) {
hp->refcount++;
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