bcache: fix a lost wake-up problem caused by mca_cannibalize_lock
This patch fix a lost wake-up problem caused by the race between
mca_cannibalize_lock and bch_cannibalize_unlock.
Consider two processes, A and B. Process A is executing
mca_cannibalize_lock, while process B takes c->btree_cache_alloc_lock
and is executing bch_cannibalize_unlock. The problem happens that after
process A executes cmpxchg and will execute prepare_to_wait. In this
timeslice process B executes wake_up, but after that process A executes
prepare_to_wait and set the state to TASK_INTERRUPTIBLE. Then process A
goes to sleep but no one will wake up it. This problem may cause bcache
device to dead.
Signed-off-by: Guoju Fang <[email protected]>
Signed-off-by: Coly Li <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 013e35a..3653faf 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -582,6 +582,7 @@ struct cache_set {
*/
wait_queue_head_t btree_cache_wait;
struct task_struct *btree_cache_alloc_lock;
+ spinlock_t btree_cannibalize_lock;
/*
* When we free a btree node, we increment the gen of the bucket the
