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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: 6c271ce2f1 ("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>
This commit is contained in:
Stefano Garzarella 2020-02-21 16:42:16 +01:00 committed by Greg Kroah-Hartman
parent b0f5f25c55
commit 8eb92c1228
1 changed files with 10 additions and 10 deletions
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20
fs/io_uring.c
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@ -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);