@@ -2481,7 +2481,14 @@ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx,
}
if (!schedule_hrtimeout(&timeout, HRTIMER_MODE_ABS))
return -ETIME;
- return 1;
+
+ /*
+ * Run task_work after scheduling. If we got woken because of
+ * task_work being processed, run it now rather than let the caller
+ * do another wait loop.
+ */
+ ret = io_run_task_work_sig(ctx);
+ return ret < 0 ? ret : 1;
}
/*
@@ -2546,6 +2553,8 @@ 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);
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> --- v2: tweak return value so we don't potentially return early from waiting on events, if we had nothing to do post returning from schedule.