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@xxxxxxxxx> --- 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
