cpu-hotplug: replace per-subsystem mutexes with get_online_cpus()

This patch converts the known per-subsystem mutexes to get_online_cpus
put_online_cpus. It also eliminates the CPU_LOCK_ACQUIRE and
CPU_LOCK_RELEASE hotplug notification events.

Signed-off-by: Gautham  R Shenoy <ego@in.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 11 insertions, 7 deletions

diff --git a/mm/slab.c b/mm/slab.c
index ff31261fd24f..40c00dacbe4b 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -730,8 +730,7 @@ static inline void init_lock_keys(void)
 #endif
 
 /*
- * 1. Guard access to the cache-chain.
- * 2. Protect sanity of cpu_online_map against cpu hotplug events
+ * Guard access to the cache-chain.
  */
 static DEFINE_MUTEX(cache_chain_mutex);
 static struct list_head cache_chain;
@@ -1331,12 +1330,11 @@ static int __cpuinit cpuup_callback(struct notifier_block *nfb,
         int err = 0;
 
         switch (action) {
-        case CPU_LOCK_ACQUIRE:
-                mutex_lock(&cache_chain_mutex);
-                break;
         case CPU_UP_PREPARE:
         case CPU_UP_PREPARE_FROZEN:
+                mutex_lock(&cache_chain_mutex);
                 err = cpuup_prepare(cpu);
+                mutex_unlock(&cache_chain_mutex);
                 break;
         case CPU_ONLINE:
         case CPU_ONLINE_FROZEN:
@@ -1373,9 +1371,8 @@ static int __cpuinit cpuup_callback(struct notifier_block *nfb,
 #endif
         case CPU_UP_CANCELED:
         case CPU_UP_CANCELED_FROZEN:
+                mutex_lock(&cache_chain_mutex);
                 cpuup_canceled(cpu);
-                break;
-        case CPU_LOCK_RELEASE:
                 mutex_unlock(&cache_chain_mutex);
                 break;
         }
@@ -2170,6 +2167,7 @@ kmem_cache_create (const char *name, size_t size, size_t align,
          * We use cache_chain_mutex to ensure a consistent view of
          * cpu_online_map as well.  Please see cpuup_callback
          */
+        get_online_cpus();
         mutex_lock(&cache_chain_mutex);
 
         list_for_each_entry(pc, &cache_chain, next) {
@@ -2396,6 +2394,7 @@ oops:
                 panic("kmem_cache_create(): failed to create slab `%s'\n",
                       name);
         mutex_unlock(&cache_chain_mutex);
+        put_online_cpus();
         return cachep;
 }
 EXPORT_SYMBOL(kmem_cache_create);
@@ -2547,9 +2546,11 @@ int kmem_cache_shrink(struct kmem_cache *cachep)
         int ret;
         BUG_ON(!cachep || in_interrupt());
 
+        get_online_cpus();
         mutex_lock(&cache_chain_mutex);
         ret = __cache_shrink(cachep);
         mutex_unlock(&cache_chain_mutex);
+        put_online_cpus();
         return ret;
 }
 EXPORT_SYMBOL(kmem_cache_shrink);
@@ -2575,6 +2576,7 @@ void kmem_cache_destroy(struct kmem_cache *cachep)
         BUG_ON(!cachep || in_interrupt());
 
         /* Find the cache in the chain of caches. */
+        get_online_cpus();
         mutex_lock(&cache_chain_mutex);
         /*
          * the chain is never empty, cache_cache is never destroyed
@@ -2584,6 +2586,7 @@ void kmem_cache_destroy(struct kmem_cache *cachep)
                 slab_error(cachep, "Can't free all objects");
                 list_add(&cachep->next, &cache_chain);
                 mutex_unlock(&cache_chain_mutex);
+                put_online_cpus();
                 return;
         }
 
@@ -2592,6 +2595,7 @@ void kmem_cache_destroy(struct kmem_cache *cachep)
 
         __kmem_cache_destroy(cachep);
         mutex_unlock(&cache_chain_mutex);
+        put_online_cpus();
 }
 EXPORT_SYMBOL(kmem_cache_destroy);