btrfs: comment the rest of implicit barriers before waitqueue_active
There are atomic operations that imply the barrier for waitqueue_active
mixed in an if-condition.
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c
index 03f8630..8077461 100644
--- a/fs/btrfs/locking.c
+++ b/fs/btrfs/locking.c
@@ -79,6 +79,9 @@
write_lock(&eb->lock);
WARN_ON(atomic_read(&eb->spinning_writers));
atomic_inc(&eb->spinning_writers);
+ /*
+ * atomic_dec_and_test implies a barrier for waitqueue_active
+ */
if (atomic_dec_and_test(&eb->blocking_writers) &&
waitqueue_active(&eb->write_lock_wq))
wake_up(&eb->write_lock_wq);
@@ -86,6 +89,9 @@
BUG_ON(atomic_read(&eb->blocking_readers) == 0);
read_lock(&eb->lock);
atomic_inc(&eb->spinning_readers);
+ /*
+ * atomic_dec_and_test implies a barrier for waitqueue_active
+ */
if (atomic_dec_and_test(&eb->blocking_readers) &&
waitqueue_active(&eb->read_lock_wq))
wake_up(&eb->read_lock_wq);
@@ -229,6 +235,9 @@
}
btrfs_assert_tree_read_locked(eb);
WARN_ON(atomic_read(&eb->blocking_readers) == 0);
+ /*
+ * atomic_dec_and_test implies a barrier for waitqueue_active
+ */
if (atomic_dec_and_test(&eb->blocking_readers) &&
waitqueue_active(&eb->read_lock_wq))
wake_up(&eb->read_lock_wq);