---

yaml
---
r: 42657
b: refs/heads/master
c: 8f5be20
h: refs/heads/master
i:
  42655: 515a99d
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: a44b56d354b49f9abb184e5a14f71889856283bb
+refs/heads/master: 8f5be20bf87da7c7c59c5cc84f630a1eca5cc99c

trunk/mm/slab.c

@@ -730,7 +730,10 @@ static inline void init_lock_keys(void)
 }
 #endif
 
-/* Guard access to the cache-chain. */
+/*
+ * 1. Guard access to the cache-chain.
+ * 2. Protect sanity of cpu_online_map against cpu hotplug events
+ */
 static DEFINE_MUTEX(cache_chain_mutex);
 static struct list_head cache_chain;
 
@@ -1230,12 +1233,18 @@ static int __cpuinit cpuup_callback(struct notifier_block *nfb,
 			kfree(shared);
 			free_alien_cache(alien);
 		}
-		mutex_unlock(&cache_chain_mutex);
 		break;
 	case CPU_ONLINE:
+		mutex_unlock(&cache_chain_mutex);
 		start_cpu_timer(cpu);
 		break;
 #ifdef CONFIG_HOTPLUG_CPU
+	case CPU_DOWN_PREPARE:
+		mutex_lock(&cache_chain_mutex);
+		break;
+	case CPU_DOWN_FAILED:
+		mutex_unlock(&cache_chain_mutex);
+		break;
 	case CPU_DEAD:
 		/*
 		 * Even if all the cpus of a node are down, we don't free the
@@ -1246,8 +1255,8 @@ static int __cpuinit cpuup_callback(struct notifier_block *nfb,
 		 * gets destroyed at kmem_cache_destroy().
 		 */
 		/* fall thru */
+#endif
 	case CPU_UP_CANCELED:
-		mutex_lock(&cache_chain_mutex);
 		list_for_each_entry(cachep, &cache_chain, next) {
 			struct array_cache *nc;
 			struct array_cache *shared;
@@ -1308,11 +1317,9 @@ static int __cpuinit cpuup_callback(struct notifier_block *nfb,
 		}
 		mutex_unlock(&cache_chain_mutex);
 		break;
-#endif
 	}
 	return NOTIFY_OK;
 bad:
-	mutex_unlock(&cache_chain_mutex);
 	return NOTIFY_BAD;
 }
 
@@ -2098,11 +2105,9 @@ kmem_cache_create (const char *name, size_t size, size_t align,
 	}
 
 	/*
-	 * Prevent CPUs from coming and going.
-	 * lock_cpu_hotplug() nests outside cache_chain_mutex
+	 * We use cache_chain_mutex to ensure a consistent view of
+	 * cpu_online_map as well.  Please see cpuup_callback
 	 */
-	lock_cpu_hotplug();
-
 	mutex_lock(&cache_chain_mutex);
 
 	list_for_each_entry(pc, &cache_chain, next) {
@@ -2325,7 +2330,6 @@ kmem_cache_create (const char *name, size_t size, size_t align,
 		panic("kmem_cache_create(): failed to create slab `%s'\n",
 		      name);
 	mutex_unlock(&cache_chain_mutex);
-	unlock_cpu_hotplug();
 	return cachep;
 }
 EXPORT_SYMBOL(kmem_cache_create);
@@ -2443,6 +2447,7 @@ static int drain_freelist(struct kmem_cache *cache,
 	return nr_freed;
 }
 
+/* Called with cache_chain_mutex held to protect against cpu hotplug */
 static int __cache_shrink(struct kmem_cache *cachep)
 {
 	int ret = 0, i = 0;
@@ -2473,9 +2478,13 @@ static int __cache_shrink(struct kmem_cache *cachep)
  */
 int kmem_cache_shrink(struct kmem_cache *cachep)
 {
+	int ret;
 	BUG_ON(!cachep || in_interrupt());
 
-	return __cache_shrink(cachep);
+	mutex_lock(&cache_chain_mutex);
+	ret = __cache_shrink(cachep);
+	mutex_unlock(&cache_chain_mutex);
+	return ret;
 }
 EXPORT_SYMBOL(kmem_cache_shrink);
 
@@ -2499,31 +2508,24 @@ void kmem_cache_destroy(struct kmem_cache *cachep)
 {
 	BUG_ON(!cachep || in_interrupt());
 
-	/* Don't let CPUs to come and go */
-	lock_cpu_hotplug();
-
 	/* Find the cache in the chain of caches. */
 	mutex_lock(&cache_chain_mutex);
 	/*
 	 * the chain is never empty, cache_cache is never destroyed
 	 */
 	list_del(&cachep->next);
-	mutex_unlock(&cache_chain_mutex);
-
 	if (__cache_shrink(cachep)) {
 		slab_error(cachep, "Can't free all objects");
-		mutex_lock(&cache_chain_mutex);
 		list_add(&cachep->next, &cache_chain);
 		mutex_unlock(&cache_chain_mutex);
-		unlock_cpu_hotplug();
 		return;
 	}
 
 	if (unlikely(cachep->flags & SLAB_DESTROY_BY_RCU))
 		synchronize_rcu();
 
 	__kmem_cache_destroy(cachep);
-	unlock_cpu_hotplug();
+	mutex_unlock(&cache_chain_mutex);
 }
 EXPORT_SYMBOL(kmem_cache_destroy);