mm/slub.c: list_lock may not be held in some circumstances

rientjes · torvalds · commit 255d0884f563 · 2014-02-10T16:01:41.000-08:00
Commit c65c187 ("slub: use lockdep_assert_held") incorrectly required that add_full() and remove_full() hold n->list_lock. The lock is only taken when kmem_cache_debug(s), since that's the only time it actually does anything. Require that the lock only be taken under such a condition. Reported-by: Larry Finger <Larry.Finger@lwfinger.net> Tested-by: Larry Finger <Larry.Finger@lwfinger.net> Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Signed-off-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/slub.c b/mm/slub.c
@@ -1004,21 +1004,19 @@ static inline void slab_free_hook(struct kmem_cache *s, void *x)
 static void add_full(struct kmem_cache *s,
 	struct kmem_cache_node *n, struct page *page)
 {
-	lockdep_assert_held(&n->list_lock);
-
 	if (!(s->flags & SLAB_STORE_USER))
 		return;
 
+	lockdep_assert_held(&n->list_lock);
 	list_add(&page->lru, &n->full);
 }
 
 static void remove_full(struct kmem_cache *s, struct kmem_cache_node *n, struct page *page)
 {
-	lockdep_assert_held(&n->list_lock);
-
 	if (!(s->flags & SLAB_STORE_USER))
 		return;
 
+	lockdep_assert_held(&n->list_lock);
 	list_del(&page->lru);
 }
 

Original file line number	Diff line number	Diff line change
`@@ -1004,21 +1004,19 @@ static inline void slab_free_hook(struct kmem_cache s, void x)`
`1004`	`1004`	`static void add_full(struct kmem_cache *s,`
`1005`	`1005`	`struct kmem_cache_node n, struct page page)`
`1006`	`1006`	`{`
`1007`		`- lockdep_assert_held(&n->list_lock);`
`1008`		`-`
`1009`	`1007`	`if (!(s->flags & SLAB_STORE_USER))`
`1010`	`1008`	`return;`
`1011`	`1009`
	`1010`	`+ lockdep_assert_held(&n->list_lock);`
`1012`	`1011`	`list_add(&page->lru, &n->full);`
`1013`	`1012`	`}`
`1014`	`1013`
`1015`	`1014`	`static void remove_full(struct kmem_cache s, struct kmem_cache_node n, struct page *page)`
`1016`	`1015`	`{`
`1017`		`- lockdep_assert_held(&n->list_lock);`
`1018`		`-`
`1019`	`1016`	`if (!(s->flags & SLAB_STORE_USER))`
`1020`	`1017`	`return;`
`1021`	`1018`
	`1019`	`+ lockdep_assert_held(&n->list_lock);`
`1022`	`1020`	`list_del(&page->lru);`
`1023`	`1021`	`}`
`1024`	`1022`