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percpu_counter: fix CPU unplug race in percpu_counter_destroy()

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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>
This commit is contained in:
Eric Dumazet
2008-12-09 13:14:11 -08:00
committed by Linus Torvalds
parent fe102c71a6
commit fd3d664fef
1 changed files with 2 additions and 2 deletions
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4
lib/percpu_counter.c
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@@ -104,13 +104,13 @@ void percpu_counter_destroy(struct percpu_counter *fbc)
if (!fbc->counters) if (!fbc->counters)
return; return;
free_percpu(fbc->counters);
fbc->counters = NULL;
#ifdef CONFIG_HOTPLUG_CPU #ifdef CONFIG_HOTPLUG_CPU
mutex_lock(&percpu_counters_lock); mutex_lock(&percpu_counters_lock);
list_del(&fbc->list); list_del(&fbc->list);
mutex_unlock(&percpu_counters_lock); mutex_unlock(&percpu_counters_lock);
#endif #endif
free_percpu(fbc->counters);
fbc->counters = NULL;
} }
EXPORT_SYMBOL(percpu_counter_destroy); EXPORT_SYMBOL(percpu_counter_destroy);