Patch "mailbox: skip complete wait event if timer expired" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

mailbox: skip complete wait event if timer expired

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mailbox-skip-complete-wait-event-if-timer-expired.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Sudeep Holla <[email protected]>
Date: Tue, 21 Mar 2017 11:30:15 +0000
Subject: mailbox: skip complete wait event if timer expired

From: Sudeep Holla <[email protected]>

commit cc6eeaa3029a6dbcb4ad41b1f92876483bd88965 upstream.

If a wait_for_completion_timeout() call returns due to a timeout, complete() can get called after returning from the wait which is incorrect and can cause subsequent transmissions on a channel to fail. Since the wait_for_completion_timeout() sees the completion variable is non-zero caused by the erroneous/spurious complete() call, and it immediately returns without waiting for the time as expected by the client.

This patch fixes the issue by skipping complete() call for the timer expiry.

---
 drivers/mailbox/mailbox.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

@@ -108,7 +108,7 @@ static void tx_tick(struct mbox_chan *ch
 	if (mssg && chan->cl->tx_done)
 		chan->cl->tx_done(chan->cl, mssg, r);
 
-	if (chan->cl->tx_block)
+	if (r != -ETIME && chan->cl->tx_block)
 		complete(&chan->tx_complete);
 }
 

@@ -272,8 +272,8 @@ int mbox_send_message(struct mbox_chan *
 
 		ret = wait_for_completion_timeout(&chan->tx_complete, wait);
 		if (ret == 0) {
-			t = -EIO;
-			tx_tick(chan, -EIO);
+			t = -ETIME;
+			tx_tick(chan, t);
 		}
 	}
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/mailbox-always-wait-in-mbox_send_message-for-blocking-tx-mode.patch queue-4.4/mailbox-skip-complete-wait-event-if-timer-expired.patch queue-4.4/mailbox-handle-empty-message-in-tx_tick.patch