percpu_counter: fix CPU unplug race in percpu_counter_destroy()

fd3d664f · Eric Dumazet <[email protected]> · 2008-12-09 13:14:11 -08:00

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 <[email protected]>
Acked-by: David S. Miller <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Mingming Cao <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Commit: fd3d664fef97cf01f8e28fe0b024ad52f3bbc1bc
Parents: fe102c71

Changes

1 files changed · +2 −2

File	Status	Add	Del	Content
lib/percpu_counter.c	modified	+2	−2	View file

lib/percpu_counter.c

View file

diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c
index a866389..71b265c 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);
 