Every receiver has CR lock on MESSAGE while processing the message. When every receiver releases ACK lock and for some reason fails to grab EX on MESSAGE resource in time, a waiting sender could queue an EX on MESSAGE instead. Now when receiver queues its up convert request on MESSAGE it will end up in a deadlock situation. Setting HEADQUE flag on MESSAGE lock resource while grabbing the EX on MESSAGE on receiver will avoid this deadlock. Any queued request by sender will be processed only after all receivers have released their EX on MESSAGE. Signed-off-by: Abhijit Bhopatkar <abhopatk@xxxxxxxxx> --- Version 2 changes from v1: Made receiver HEADQUE rather than making sender NOQUEUE, also get rid of goto pollution Minimaly tested on three node cluster, operations create,assemble tested on two a shared raid disks. drivers/md/md-cluster.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/drivers/md/md-cluster.c b/drivers/md/md-cluster.c index fcfc4b9..cb76c0f 100644 --- a/drivers/md/md-cluster.c +++ b/drivers/md/md-cluster.c @@ -480,8 +480,17 @@ static void recv_daemon(struct md_thread *thread) /*release CR on ack_lockres*/ dlm_unlock_sync(ack_lockres); - /*up-convert to EX on message_lockres*/ + + /* up-convert to EX on message_lockres + * Since another sender might already be ready to send data. + * Use DLM_LKF_HEADQUE to move this lock request ahead of + * that sender. + */ + + message_lockres->flags |= DLM_LKF_HEADQUE; dlm_lock_sync(message_lockres, DLM_LOCK_EX); + message_lockres->flags &= ~DLM_LKF_HEADQUE; + /*get CR on ack_lockres again*/ dlm_lock_sync(ack_lockres, DLM_LOCK_CR); /*release CR on message_lockres*/ -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
