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btrfs: Add WARN_ON() for double lock in btrfs_tree_lock() 

When a task trying to double lock a extent buffer, there are no
lockdep warning about it because this lock may be in "blocking_lock"
state, and make us hard to debug.

This patch add a WARN_ON() for above condition, it can not report
all deadlock cases(as lock between tasks), but at least helps us
some.

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
steinar/wifi_calib_4_9_kernel
Zhaolei 2015-08-06 22:39:36 +08:00 committed by Chris Mason
parent 9ed0dea09f
commit 166f66d0bc
1 changed files with 1 additions and 0 deletions
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fs/btrfs/locking.c
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@ -241,6 +241,7 @@ 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);