--- drivers/md/raid10.c

+++ drivers/md/raid10.c

@@ -824,11 +824,29 @@ static int make_request(struct request_q

*/

bp = bio_split(bio,

chunk_sects - (bio->bi_sector & (chunk_sects - 1)) );

+

+ /* Each of these 'make_request' calls will call 'wait_barrier'.

+ * If the first succeeds but the second blocks due to the resync

+ * thread raising the barrier, we will deadlock because the

+ * IO to the underlying device will be queued in generic_make_request

+ * and will never complete, so will never reduce nr_pending.

+ * So increment nr_waiting here so no new raise_barriers will

+ * succeed, and so the second wait_barrier cannot block.

+ */

+ spin_lock_irq(&conf->resync_lock);

+ conf->nr_waiting++;

+ spin_unlock_irq(&conf->resync_lock);

+

if (make_request(q, &bp->bio1))

generic_make_request(&bp->bio1);

if (make_request(q, &bp->bio2))

generic_make_request(&bp->bio2);

+ spin_lock_irq(&conf->resync_lock);

+ conf->nr_waiting--;

+ wake_up(&conf->wait_barrier);

+ spin_unlock_irq(&conf->resync_lock);

+

bio_pair_release(bp);

return 0;

bad_map: