From fd3d664fef97cf01f8e28fe0b024ad52f3bbc1bc Mon Sep 17 00:00:00 2001
From: Eric Dumazet <dada1@cosmosbay.com>
Date: Tue, 9 Dec 2008 13:14:11 -0800
Subject: percpu_counter: fix CPU unplug race in percpu_counter_destroy()

We should first delete the counter from percpu_counters list
before freeing memory, or a percpu_counter_hotcpu_callback()
could dereference a NULL pointer.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Acked-by: David S. Miller <davem@davemloft.net>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 lib/percpu_counter.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'lib/percpu_counter.c')

diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c
index a8663890a88c..71b265c330ce 100644
--- a/lib/percpu_counter.c
+++ b/lib/percpu_counter.c
@@ -104,13 +104,13 @@ void percpu_counter_destroy(struct percpu_counter *fbc)
 	if (!fbc->counters)
 		return;
 
-	free_percpu(fbc->counters);
-	fbc->counters = NULL;
 #ifdef CONFIG_HOTPLUG_CPU
 	mutex_lock(&percpu_counters_lock);
 	list_del(&fbc->list);
 	mutex_unlock(&percpu_counters_lock);
 #endif
+	free_percpu(fbc->counters);
+	fbc->counters = NULL;
 }
 EXPORT_SYMBOL(percpu_counter_destroy);
 
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