From f31b617a9cfe6498b9ebc27187fee5385c17e337 Mon Sep 17 00:00:00 2001
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>

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 7de9868..b9c39b5 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -81,9 +81,11 @@ static DEFINE_PER_CPU(struct hotplug_pcp, 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) {
 		hp->refcount++;
-- 
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