This is a note to let you know that I've just added the patch titled
io_uring: fix io_sq_thread no schedule when busy
to the 5.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
io_uring-fix-io_sq_thread-no-schedule-when-busy.patch
and it can be found in the queue-5.7 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 4facbc6278d7946f8f884a73a288270194e98c6c
Author: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
Date: Tue Jun 23 19:34:06 2020 +0800
io_uring: fix io_sq_thread no schedule when busy
[ Upstream commit b772f07add1c0b22e02c0f1e96f647560679d3a9 ]
When the user consumes and generates sqe at a fast rate,
io_sqring_entries can always get sqe, and ret will not be equal to -EBUSY,
so that io_sq_thread will never call cond_resched or schedule, and then
we will get the following system error prompt:
rcu: INFO: rcu_sched self-detected stall on CPU
or
watchdog: BUG: soft lockup-CPU#23 stuck for 112s! [io_uring-sq:1863]
This patch checks whether need to call cond_resched() by checking
the need_resched() function every cycle.
Suggested-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/io_uring.c b/fs/io_uring.c
index bb74e45941af2..63a456921903e 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6084,7 +6084,7 @@ static int io_sq_thread(void *data)
* If submit got -EBUSY, flag us as needing the application
* to enter the kernel to reap and flush events.
*/
- if (!to_submit || ret == -EBUSY) {
+ if (!to_submit || ret == -EBUSY || need_resched()) {
/*
* Drop cur_mm before scheduling, we can't hold it for
* long periods (or over schedule()). Do this before
@@ -6100,7 +6100,7 @@ static int io_sq_thread(void *data)
* more IO, we should wait for the application to
* reap events and wake us up.
*/
- if (!list_empty(&ctx->poll_list) ||
+ if (!list_empty(&ctx->poll_list) || need_resched() ||
(!time_after(jiffies, timeout) && ret != -EBUSY &&
!percpu_ref_is_dying(&ctx->refs))) {
if (current->task_works)
