switch the protection of percpu_counter list to spinlock

... making percpu_counter_destroy() non-blocking

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c
index f8a3f1a..ba6085d 100644 (file)
--- a/lib/percpu_counter.c
+++ b/lib/percpu_counter.c
@@ -12,7 +12,7 @@
 
 #ifdef CONFIG_HOTPLUG_CPU
 static LIST_HEAD(percpu_counters);
-static DEFINE_MUTEX(percpu_counters_lock);
+static DEFINE_SPINLOCK(percpu_counters_lock);
 #endif
 
 #ifdef CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER
@@ -123,9 +123,9 @@ int __percpu_counter_init(struct percpu_counter *fbc, s64 amount,
 
 #ifdef CONFIG_HOTPLUG_CPU
        INIT_LIST_HEAD(&fbc->list);
-       mutex_lock(&percpu_counters_lock);
+       spin_lock(&percpu_counters_lock);
        list_add(&fbc->list, &percpu_counters);
-       mutex_unlock(&percpu_counters_lock);
+       spin_unlock(&percpu_counters_lock);
 #endif
        return 0;
 }
@@ -139,9 +139,9 @@ void percpu_counter_destroy(struct percpu_counter *fbc)
        debug_percpu_counter_deactivate(fbc);
 
 #ifdef CONFIG_HOTPLUG_CPU
-       mutex_lock(&percpu_counters_lock);
+       spin_lock(&percpu_counters_lock);
        list_del(&fbc->list);
-       mutex_unlock(&percpu_counters_lock);
+       spin_unlock(&percpu_counters_lock);
 #endif
        free_percpu(fbc->counters);
        fbc->counters = NULL;
@@ -170,7 +170,7 @@ static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb,
                return NOTIFY_OK;
 
        cpu = (unsigned long)hcpu;
-       mutex_lock(&percpu_counters_lock);
+       spin_lock(&percpu_counters_lock);
        list_for_each_entry(fbc, &percpu_counters, list) {
                s32 *pcount;
                unsigned long flags;
@@ -181,7 +181,7 @@ static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb,
                *pcount = 0;
                raw_spin_unlock_irqrestore(&fbc->lock, flags);
        }
-       mutex_unlock(&percpu_counters_lock);
+       spin_unlock(&percpu_counters_lock);
 #endif
        return NOTIFY_OK;
 }