lkml.org 
[lkml]   [2020]   [Feb]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 5.5 134/150] io_uring: prevent sq_thread from spinning when it should stop
Date
From: Stefano Garzarella <sgarzare@redhat.com>

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@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
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);


\
 
 \ /
  Last update: 2020-02-27 15:18    [W:0.606 / U:0.088 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site