[PATCH 2/2] io_uring: include task_work run after scheduling in wait for events

[Jens Axboe <axboe@kernel.dk>]

It's quite possible that we got woken up because task_work was queued,
and we need to process this task_work to generate the events waited for.
If we return to the wait loop without running task_work, we'll end up
adding the task to the waitqueue again, only to call
io_cqring_wait_schedule() again which will run the task_work. This is
less efficient than it could be, as it requires adding to the cq_wait
queue again. It also triggers the wakeup path for completions as
cq_wait is now non-empty with the task itself, and it'll require another
lock grab and deletion to remove ourselves from the waitqueue.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 io_uring/io_uring.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 16a323a9ff70..945bea3e8e5f 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -2481,7 +2481,7 @@ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx,
 	}
 	if (!schedule_hrtimeout(&timeout, HRTIMER_MODE_ABS))
 		return -ETIME;
-	return 1;
+	return io_run_task_work_sig(ctx);
 }
 
 /*
@@ -2546,6 +2546,8 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
 		prepare_to_wait_exclusive(&ctx->cq_wait, &iowq.wq,
 						TASK_INTERRUPTIBLE);
 		ret = io_cqring_wait_schedule(ctx, &iowq, timeout);
+		if (__io_cqring_events_user(ctx) >= min_events)
+			break;
 		cond_resched();
 	} while (ret > 0);
 
-- 
2.35.1