---

yaml
---
r: 373739
b: refs/heads/master
c: 7cccd80
h: refs/heads/master
i:
  373737: adcea39
  373735: 67e950c
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 4d7868e6475d478172581828021bd8a356726679
+refs/heads/master: 7cccd80b4397699902aced1ad3d692d384aaab77

trunk/mm/slub.c

@@ -2332,13 +2332,18 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s,
 
 	s = memcg_kmem_get_cache(s, gfpflags);
 redo:
-
 	/*
 	 * Must read kmem_cache cpu data via this cpu ptr. Preemption is
 	 * enabled. We may switch back and forth between cpus while
 	 * reading from one cpu area. That does not matter as long
 	 * as we end up on the original cpu again when doing the cmpxchg.
+	 *
+	 * Preemption is disabled for the retrieval of the tid because that
+	 * must occur from the current processor. We cannot allow rescheduling
+	 * on a different processor between the determination of the pointer
+	 * and the retrieval of the tid.
 	 */
+	preempt_disable();
 	c = __this_cpu_ptr(s->cpu_slab);
 
 	/*
@@ -2348,7 +2353,7 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s,
 	 * linked list in between.
 	 */
 	tid = c->tid;
-	barrier();
+	preempt_enable();
 
 	object = c->freelist;
 	page = c->page;
@@ -2595,10 +2600,11 @@ static __always_inline void slab_free(struct kmem_cache *s,
 	 * data is retrieved via this pointer. If we are on the same cpu
 	 * during the cmpxchg then the free will succedd.
 	 */
+	preempt_disable();
 	c = __this_cpu_ptr(s->cpu_slab);
 
 	tid = c->tid;
-	barrier();
+	preempt_enable();
 
 	if (likely(page == c->page)) {
 		set_freepointer(s, object, c->freelist);