From: Stefano Garzarella <sgarzare@xxxxxxxxxx>
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: 6c271ce2f1d5 ("io_uring: add submission polling")
Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/io_uring.c | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3909,6 +3909,18 @@ static int io_sq_thread(void *data)
*/
if (!to_submit || ret == -EBUSY) {
/*
+ * Drop cur_mm before scheduling, we can't hold it for
+ * long periods (or over schedule()). Do this before
+ * adding ourselves to the waitqueue, as the unuse/drop
+ * may sleep.
+ */
+ if (cur_mm) {
+ unuse_mm(cur_mm);
+ mmput(cur_mm);
+ cur_mm = NULL;
+ }
+
+ /*
* We're polling. If we're within the defined idle
* period, then let us spin without work before going
* to sleep. The exception is if we got EBUSY doing
@@ -3922,18 +3934,6 @@ static int io_sq_thread(void *data)
continue;
}
- /*
- * Drop cur_mm before scheduling, we can't hold it for
- * long periods (or over schedule()). Do this before
- * adding ourselves to the waitqueue, as the unuse/drop
- * may sleep.
- */
- if (cur_mm) {
- unuse_mm(cur_mm);
- mmput(cur_mm);
- cur_mm = NULL;
- }
-
prepare_to_wait(&ctx->sqo_wait, &wait,
TASK_INTERRUPTIBLE);
