From d5627acba9ae584cf4928af19f7ddf5f6837de32 Mon Sep 17 00:00:00 2001 From: Roland Dreier Date: Wed, 31 Oct 2012 09:16:46 -0700 Subject: iscsi-target: Fix missed wakeup race in TX thread The sleeping code in iscsi_target_tx_thread() is susceptible to the classic missed wakeup race: - TX thread finishes handle_immediate_queue() and handle_response_queue(), thinks both queues are empty. - Another thread adds a queue entry and does wake_up_process(), which does nothing because the TX thread is still awake. - TX thread does schedule_timeout() and sleeps forever. In practice this can kill an iSCSI connection if for example an initiator does single-threaded writes and the target misses the wakeup window when queueing an R2T; in this case the connection will be stuck until the initiator loses patience and does some task management operation (or kills the connection entirely). Fix this by converting to wait_event_interruptible(), which does not suffer from this sort of race. Signed-off-by: Roland Dreier Cc: Andy Grover Cc: Hannes Reinecke Cc: Christoph Hellwig Cc: stable@vger.kernel.org Signed-off-by: Nicholas Bellinger --- drivers/target/iscsi/iscsi_target.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'drivers/target/iscsi/iscsi_target.c') diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c index d6ce2182e67..035c2c76253 100644 --- a/drivers/target/iscsi/iscsi_target.c +++ b/drivers/target/iscsi/iscsi_target.c @@ -3719,7 +3719,9 @@ restart: */ iscsit_thread_check_cpumask(conn, current, 1); - schedule_timeout_interruptible(MAX_SCHEDULE_TIMEOUT); + wait_event_interruptible(conn->queues_wq, + !iscsit_conn_all_queues_empty(conn) || + ts->status == ISCSI_THREAD_SET_RESET); if ((ts->status == ISCSI_THREAD_SET_RESET) || signal_pending(current)) -- cgit v1.2.3-70-g09d2