From 4bada93e5f0059553d3bede60859b7934de4a903 Mon Sep 17 00:00:00 2001
From: Ravikiran G Thirumalai <kiran@scalex86.org>
Date: Wed, 6 Dec 2006 20:32:14 -0800
Subject: [PATCH] --- yaml --- r: 42657 b: refs/heads/master c:
 8f5be20bf87da7c7c59c5cc84f630a1eca5cc99c h: refs/heads/master i:   42655:
 515a99de3c2a7ec1feb95f28e471fadc30110fd4 v: v3

---
 [refs]          |  2 +-
 trunk/mm/slab.c | 40 +++++++++++++++++++++-------------------
 2 files changed, 22 insertions(+), 20 deletions(-)

diff --git a/[refs] b/[refs]
index 31c33fc447b3..96bc7b1aebe9 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: a44b56d354b49f9abb184e5a14f71889856283bb
+refs/heads/master: 8f5be20bf87da7c7c59c5cc84f630a1eca5cc99c
diff --git a/trunk/mm/slab.c b/trunk/mm/slab.c
index ff60a94142f9..3318252f657f 100644
--- a/trunk/mm/slab.c
+++ b/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);
 
@@ -2499,23 +2508,16 @@ 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;
 	}
 
@@ -2523,7 +2525,7 @@ void kmem_cache_destroy(struct kmem_cache *cachep)
 		synchronize_rcu();
 
 	__kmem_cache_destroy(cachep);
-	unlock_cpu_hotplug();
+	mutex_unlock(&cache_chain_mutex);
 }
 EXPORT_SYMBOL(kmem_cache_destroy);