[PATCH] slab: fix drain_array() so that it works correctly with the shared_array
The list_lock also protects the shared array and we call drain_array() with
the shared array. Therefore we cannot go as far as I wanted to but have to
take the lock in a way so that it also protects the array_cache in
drain_pages.
(Note: maybe we should make the array_cache locking more consistent? I.e.
always take the array cache lock for shared arrays and disable interrupts
for the per cpu arrays?)
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/mm/slab.c b/mm/slab.c
index 3274144..6b691ec 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3521,7 +3521,8 @@
/*
* Drain an array if it contains any elements taking the l3 lock only if
- * necessary.
+ * necessary. Note that the l3 listlock also protects the array_cache
+ * if drain_array() is used on the shared array.
*/
void drain_array(struct kmem_cache *cachep, struct kmem_list3 *l3,
struct array_cache *ac, int force, int node)
@@ -3532,16 +3533,18 @@
return;
if (ac->touched && !force) {
ac->touched = 0;
- } else if (ac->avail) {
- tofree = force ? ac->avail : (ac->limit + 4) / 5;
- if (tofree > ac->avail)
- tofree = (ac->avail + 1) / 2;
+ } else {
spin_lock_irq(&l3->list_lock);
- free_block(cachep, ac->entry, tofree, node);
+ if (ac->avail) {
+ tofree = force ? ac->avail : (ac->limit + 4) / 5;
+ if (tofree > ac->avail)
+ tofree = (ac->avail + 1) / 2;
+ free_block(cachep, ac->entry, tofree, node);
+ ac->avail -= tofree;
+ memmove(ac->entry, &(ac->entry[tofree]),
+ sizeof(void *) * ac->avail);
+ }
spin_unlock_irq(&l3->list_lock);
- ac->avail -= tofree;
- memmove(ac->entry, &(ac->entry[tofree]),
- sizeof(void *) * ac->avail);
}
}