Commit 8eb92c12 authored Feb 21, 2020 by Stefano Garzarella Committed by Greg Kroah-Hartman Feb 28, 2020

io_uring: prevent sq_thread from spinning when it should stop



commit 7143b5ac5750f404ff3a594b34fdf3fc2f99f828 upstream.

This patch drops 'cur_mm' before calling cond_resched(), to prevent
the sq_thread from spinning even when the user process is finished.

Before this patch, if the user process ended without closing the
io_uring fd, the sq_thread continues to spin until the
'sq_thread_idle' timeout ends.

In the worst case where the 'sq_thread_idle' parameter is bigger than
INT_MAX, the sq_thread will spin forever.

Fixes: 6c271ce2 ("io_uring: add submission polling")
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent b0f5f25c

fs/io_uring.c

+10 −10

Original line number	Diff line number	Diff line
		@@ -2731,16 +2731,6 @@ static int io_sq_thread(void *data)

		to_submit = io_sqring_entries(ctx);
		if (!to_submit) {
		/*
		* We're polling. If we're within the defined idle
		* period, then let us spin without work before going
		* to sleep.
		*/
		if (inflight \|\| !time_after(jiffies, timeout)) {
		cond_resched();
		continue;
		}

		/*
		* Drop cur_mm before scheduling, we can't hold it for
		* long periods (or over schedule()). Do this before
		@@ -2753,6 +2743,16 @@ static int io_sq_thread(void *data)
		cur_mm = NULL;
		}

		/*
		* We're polling. If we're within the defined idle
		* period, then let us spin without work before going
		* to sleep.
		*/
		if (inflight \|\| !time_after(jiffies, timeout)) {
		cond_resched();
		continue;
		}

		prepare_to_wait(&ctx->sqo_wait, &wait,
		TASK_INTERRUPTIBLE);