1 files changed, 70 insertions, 20 deletions

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 45a3928544ce..206e0e2ace53 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -66,7 +66,8 @@ static struct tracer_flags blk_tracer_flags = {
 };
 
 /* Global reference count of probes */
-static atomic_t blk_probes_ref = ATOMIC_INIT(0);
+static DEFINE_MUTEX(blk_probe_mutex);
+static int blk_probes_ref;
 
 static void blk_register_tracepoints(void);
 static void blk_unregister_tracepoints(void);
@@ -329,14 +330,29 @@ static void blk_trace_free(struct blk_trace *bt)
         kfree(bt);
 }
 
+static void get_probe_ref(void)
+{
+        mutex_lock(&blk_probe_mutex);
+        if (++blk_probes_ref == 1)
+                blk_register_tracepoints();
+        mutex_unlock(&blk_probe_mutex);
+}
+
+static void put_probe_ref(void)
+{
+        mutex_lock(&blk_probe_mutex);
+        if (!--blk_probes_ref)
+                blk_unregister_tracepoints();
+        mutex_unlock(&blk_probe_mutex);
+}
+
 static void blk_trace_cleanup(struct blk_trace *bt)
 {
         blk_trace_free(bt);
-        if (atomic_dec_and_test(&blk_probes_ref))
-                blk_unregister_tracepoints();
+        put_probe_ref();
 }
 
-int blk_trace_remove(struct request_queue *q)
+static int __blk_trace_remove(struct request_queue *q)
 {
         struct blk_trace *bt;
 
@@ -349,6 +365,17 @@ int blk_trace_remove(struct request_queue *q)
 
         return 0;
 }
+
+int blk_trace_remove(struct request_queue *q)
+{
+        int ret;
+
+        mutex_lock(&q->blk_trace_mutex);
+        ret = __blk_trace_remove(q);
+        mutex_unlock(&q->blk_trace_mutex);
+
+        return ret;
+}
 EXPORT_SYMBOL_GPL(blk_trace_remove);
 
 static ssize_t blk_dropped_read(struct file *filp, char __user *buffer,
@@ -538,8 +565,7 @@ static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
         if (cmpxchg(&q->blk_trace, NULL, bt))
                 goto err;
 
-        if (atomic_inc_return(&blk_probes_ref) == 1)
-                blk_register_tracepoints();
+        get_probe_ref();
 
         ret = 0;
 err:
@@ -550,9 +576,8 @@ err:
         return ret;
 }
 
-int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
-                    struct block_device *bdev,
-                    char __user *arg)
+static int __blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
+                             struct block_device *bdev, char __user *arg)
 {
         struct blk_user_trace_setup buts;
         int ret;
@@ -571,6 +596,19 @@ int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
         }
         return 0;
 }
+
+int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
+                    struct block_device *bdev,
+                    char __user *arg)
+{
+        int ret;
+
+        mutex_lock(&q->blk_trace_mutex);
+        ret = __blk_trace_setup(q, name, dev, bdev, arg);
+        mutex_unlock(&q->blk_trace_mutex);
+
+        return ret;
+}
 EXPORT_SYMBOL_GPL(blk_trace_setup);
 
 #if defined(CONFIG_COMPAT) && defined(CONFIG_X86_64)
@@ -607,7 +645,7 @@ static int compat_blk_trace_setup(struct request_queue *q, char *name,
 }
 #endif
 
-int blk_trace_startstop(struct request_queue *q, int start)
+static int __blk_trace_startstop(struct request_queue *q, int start)
 {
         int ret;
         struct blk_trace *bt = q->blk_trace;
@@ -646,6 +684,17 @@ int blk_trace_startstop(struct request_queue *q, int start)
 
         return ret;
 }
+
+int blk_trace_startstop(struct request_queue *q, int start)
+{
+        int ret;
+
+        mutex_lock(&q->blk_trace_mutex);
+        ret = __blk_trace_startstop(q, start);
+        mutex_unlock(&q->blk_trace_mutex);
+
+        return ret;
+}
 EXPORT_SYMBOL_GPL(blk_trace_startstop);
 
 /*
@@ -676,7 +725,7 @@ int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
         switch (cmd) {
         case BLKTRACESETUP:
                 bdevname(bdev, b);
-                ret = blk_trace_setup(q, b, bdev->bd_dev, bdev, arg);
+                ret = __blk_trace_setup(q, b, bdev->bd_dev, bdev, arg);
                 break;
 #if defined(CONFIG_COMPAT) && defined(CONFIG_X86_64)
         case BLKTRACESETUP32:
@@ -687,10 +736,10 @@ int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
         case BLKTRACESTART:
                 start = 1;
         case BLKTRACESTOP:
-                ret = blk_trace_startstop(q, start);
+                ret = __blk_trace_startstop(q, start);
                 break;
         case BLKTRACETEARDOWN:
-                ret = blk_trace_remove(q);
+                ret = __blk_trace_remove(q);
                 break;
         default:
                 ret = -ENOTTY;
@@ -708,10 +757,14 @@ int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
  **/
 void blk_trace_shutdown(struct request_queue *q)
 {
+        mutex_lock(&q->blk_trace_mutex);
+
         if (q->blk_trace) {
-                blk_trace_startstop(q, 0);
-                blk_trace_remove(q);
+                __blk_trace_startstop(q, 0);
+                __blk_trace_remove(q);
         }
+
+        mutex_unlock(&q->blk_trace_mutex);
 }
 
 #ifdef CONFIG_BLK_CGROUP
@@ -1558,9 +1611,7 @@ static int blk_trace_remove_queue(struct request_queue *q)
         if (bt == NULL)
                 return -EINVAL;
 
-        if (atomic_dec_and_test(&blk_probes_ref))
-                blk_unregister_tracepoints();
-
+        put_probe_ref();
         blk_trace_free(bt);
         return 0;
 }
@@ -1591,8 +1642,7 @@ static int blk_trace_setup_queue(struct request_queue *q,
         if (cmpxchg(&q->blk_trace, NULL, bt))
                 goto free_bt;
 
-        if (atomic_inc_return(&blk_probes_ref) == 1)
-                blk_register_tracepoints();
+        get_probe_ref();
         return 0;
 
 free_bt: