linux-kernel - [PATCH 5.13 144/223] io_uring: Fix race condition when sqp thread goes to sleep

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Date:   Mon, 26 Jul 2021 17:38:56 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Olivier Langlois <olivier@...llion01.com>,
        Pavel Begunkov <asml.silence@...il.com>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 5.13 144/223] io_uring: Fix race condition when sqp thread goes to sleep

From: Olivier Langlois <olivier@...llion01.com>

commit 997135017716c33f3405e86cca5da9567b40a08e upstream.

If an asynchronous completion happens before the task is preparing
itself to wait and set its state to TASK_INTERRUPTIBLE, the completion
will not wake up the sqp thread.

Cc: stable@...r.kernel.org
Signed-off-by: Olivier Langlois <olivier@...llion01.com>
Reviewed-by: Pavel Begunkov <asml.silence@...il.com>
Link: https://lore.kernel.org/r/d1419dc32ec6a97b453bee34dc03fa6a02797142.1624473200.git.olivier@trillion01.com
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/io_uring.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6876,7 +6876,8 @@ static int io_sq_thread(void *data)
 		}
 
 		prepare_to_wait(&sqd->wait, &wait, TASK_INTERRUPTIBLE);
-		if (!test_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state)) {
+		if (!test_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state) &&
+		    !io_run_task_work()) {
 			list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
 				io_ring_set_wakeup_flag(ctx);