Merge remote-tracking branch 'ftrace/for-next'

[karo-tx-linux.git] / kernel / trace / blktrace.c

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index b2fcf472774e7d2487eb79f1b46013412eb6b434..a990824c86044779c089156daea170412cc84e8e 100644 (file)
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -437,7 +437,7 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
                       struct block_device *bdev,
                       struct blk_user_trace_setup *buts)
 {
-       struct blk_trace *old_bt, *bt = NULL;
+       struct blk_trace *bt = NULL;
        struct dentry *dir = NULL;
        int ret;
 
@@ -519,11 +519,8 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
        bt->trace_state = Blktrace_setup;
 
        ret = -EBUSY;
-       old_bt = xchg(&q->blk_trace, bt);
-       if (old_bt) {
-               (void) xchg(&q->blk_trace, old_bt);
+       if (cmpxchg(&q->blk_trace, NULL, bt))
                goto err;
-       }
 
        if (atomic_inc_return(&blk_probes_ref) == 1)
                blk_register_tracepoints();
@@ -1482,7 +1479,7 @@ static int blk_trace_remove_queue(struct request_queue *q)
 static int blk_trace_setup_queue(struct request_queue *q,
                                 struct block_device *bdev)
 {
-       struct blk_trace *old_bt, *bt = NULL;
+       struct blk_trace *bt = NULL;
        int ret = -ENOMEM;
 
        bt = kzalloc(sizeof(*bt), GFP_KERNEL);
@@ -1498,12 +1495,9 @@ static int blk_trace_setup_queue(struct request_queue *q,
 
        blk_trace_setup_lba(bt, bdev);
 
-       old_bt = xchg(&q->blk_trace, bt);
-       if (old_bt != NULL) {
-               (void)xchg(&q->blk_trace, old_bt);
-               ret = -EBUSY;
+       ret = -EBUSY;
+       if (cmpxchg(&q->blk_trace, NULL, bt))
                goto free_bt;
-       }
 
        if (atomic_inc_return(&blk_probes_ref) == 1)
                blk_register_tracepoints();