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* [PATCH v2] io_uring: fix io_sq_thread no schedule when busy
       [not found] <a932f437e5337cbfb42db660473fa55fa7aff9f6.1592804776.git.xuanzhuo@linux.alibaba.com>
@ 2020-06-23 11:34 ` Xuan Zhuo
  2020-06-23 17:54   ` Jens Axboe
  0 siblings, 1 reply; 2+ messages in thread
From: Xuan Zhuo @ 2020-06-23 11:34 UTC (permalink / raw)
  To: io-uring, [email protected]; +Cc: Dust.li

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 <[email protected]>
Signed-off-by: Xuan Zhuo <[email protected]>
---
 fs/io_uring.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index a78201b..9de9db7 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6011,7 +6011,7 @@ 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
@@ -6027,7 +6027,7 @@ 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)
-- 
1.8.3.1


^ permalink raw reply related	[flat|nested] 2+ messages in thread

* Re: [PATCH v2] io_uring: fix io_sq_thread no schedule when busy
  2020-06-23 11:34 ` [PATCH v2] io_uring: fix io_sq_thread no schedule when busy Xuan Zhuo
@ 2020-06-23 17:54   ` Jens Axboe
  0 siblings, 0 replies; 2+ messages in thread
From: Jens Axboe @ 2020-06-23 17:54 UTC (permalink / raw)
  To: Xuan Zhuo, io-uring; +Cc: Dust.li

On 6/23/20 5:34 AM, Xuan Zhuo wrote:
> 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.

Applied, thanks.

-- 
Jens Axboe


^ permalink raw reply	[flat|nested] 2+ messages in thread

end of thread, other threads:[~2020-06-23 17:54 UTC | newest]

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2020-06-23 11:34 ` [PATCH v2] io_uring: fix io_sq_thread no schedule when busy Xuan Zhuo
2020-06-23 17:54   ` Jens Axboe

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