linux-kernel - [PATCH 08/18] drbd: fix a race stopping the worker thread

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Date:	Mon, 30 Jun 2014 17:52:57 +0200
From:	Philipp Reisner <philipp.reisner@...bit.com>
To:	linux-kernel@...r.kernel.org, Jens Axboe <axboe@...nel.dk>
Cc:	drbd-dev@...ts.linbit.com
Subject: [PATCH 08/18] drbd: fix a race stopping the worker thread

From: Lars Ellenberg <lars.ellenberg@...bit.com>

We may implicitly call drbd_send() from inside wait_for_work(),
via maybe_send_barrier().

If the "stop" signal was send just before that, drbd_send() would call
flush_signals(), and we would run an unbounded schedule() afterwards.

Fix: check for thread_state == RUNNING before we schedule()

Signed-off-by: Philipp Reisner <philipp.reisner@...bit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@...bit.com>
---
 drivers/block/drbd/drbd_worker.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index 5915885..47bc840 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -1930,6 +1930,9 @@ static void wait_for_work(struct drbd_connection *connection, struct list_head *
 		if (send_barrier)
 			maybe_send_barrier(connection,
 					connection->send.current_epoch_nr + 1);
+		/* drbd_send() may have called flush_signals() */
+		if (get_t_state(&connection->worker) != RUNNING)
+			break;
 		schedule();
 		/* may be woken up for other things but new work, too,
 		 * e.g. if the current epoch got closed.
-- 
1.9.1

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