public inbox for [email protected]
 help / color / mirror / Atom feed
* [PATCH v2] io_uring: clear TIF_NOTIFY_SIGNAL if set and task_work not available
@ 2022-11-25 16:51 Jens Axboe
  0 siblings, 0 replies; only message in thread
From: Jens Axboe @ 2022-11-25 16:51 UTC (permalink / raw)
  To: io-uring

If we have io-wq or SQPOLL setting the task_work notify signal but the
task itself doesn't have task_work to process, we don't clear the
flag and hence will enter a repeated check loop if we're waiting on
events or file/buf references to go away.

This was introduced in a recent patch which eliminated gating the
task_work run on just that flag, but that fix meant that we know don't
clear the flag if the task itsel doesn't have task_work to run.

Cc: [email protected]
Fixes: 46a525e199e4 ("io_uring: don't gate task_work run on TIF_NOTIFY_SIGNAL")
Signed-off-by: Jens Axboe <[email protected]>

---

V2
	- Add comment
	- Keep the clear-if-set logic, just move it outside the tw check

diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
index cef5ff924e63..a70f8ec88bf3 100644
--- a/io_uring/io_uring.h
+++ b/io_uring/io_uring.h
@@ -238,9 +238,16 @@ static inline unsigned int io_sqring_entries(struct io_ring_ctx *ctx)
 
 static inline int io_run_task_work(void)
 {
+	/*
+	 * Always check-and-clear the task_work notification signal. The
+	 * current task may have it set if io-wq or SQPOLL sets it, but not
+	 * have any task_work itself. This can prevent the current task from
+	 * waiting on events efficiently, as interruptible sleeps will turn
+	 * into busy loops.
+	 */
+	if (test_thread_flag(TIF_NOTIFY_SIGNAL))
+		clear_notify_signal();
 	if (task_work_pending(current)) {
-		if (test_thread_flag(TIF_NOTIFY_SIGNAL))
-			clear_notify_signal();
 		__set_current_state(TASK_RUNNING);
 		task_work_run();
 		return 1;

-- 
Jens Axboe

^ permalink raw reply related	[flat|nested] only message in thread

only message in thread, other threads:[~2022-11-25 16:51 UTC | newest]

Thread overview: (only message) (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2022-11-25 16:51 [PATCH v2] io_uring: clear TIF_NOTIFY_SIGNAL if set and task_work not available Jens Axboe

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox