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Diffstat (limited to 'kernel/fs/btrfs/locking.c')
-rw-r--r--kernel/fs/btrfs/locking.c13
1 files changed, 13 insertions, 0 deletions
diff --git a/kernel/fs/btrfs/locking.c b/kernel/fs/btrfs/locking.c
index f8229ef1b..8077461fc 100644
--- a/kernel/fs/btrfs/locking.c
+++ b/kernel/fs/btrfs/locking.c
@@ -79,6 +79,9 @@ void btrfs_clear_lock_blocking_rw(struct extent_buffer *eb, int rw)
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 @@ void btrfs_clear_lock_blocking_rw(struct extent_buffer *eb, int rw)
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 @@ void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb)
}
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);
@@ -241,6 +250,7 @@ void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb)
*/
void btrfs_tree_lock(struct extent_buffer *eb)
{
+ WARN_ON(eb->lock_owner == current->pid);
again:
wait_event(eb->read_lock_wq, atomic_read(&eb->blocking_readers) == 0);
wait_event(eb->write_lock_wq, atomic_read(&eb->blocking_writers) == 0);
@@ -279,6 +289,9 @@ void btrfs_tree_unlock(struct extent_buffer *eb)
if (blockers) {
WARN_ON(atomic_read(&eb->spinning_writers));
atomic_dec(&eb->blocking_writers);
+ /*
+ * Make sure counter is updated before we wake up waiters.
+ */
smp_mb();
if (waitqueue_active(&eb->write_lock_wq))
wake_up(&eb->write_lock_wq);