io_uring: implement our own schedule timeout handling

In preparation for having two distinct timeouts and avoid waking the
task if we don't need to.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/io_uring.c

@@ -2350,6 +2350,34 @@ static bool current_pending_io(void)
 	return percpu_counter_read_positive(&tctx->inflight);
 }
 
+static enum hrtimer_restart io_cqring_timer_wakeup(struct hrtimer *timer)
+{
+	struct io_wait_queue *iowq = container_of(timer, struct io_wait_queue, t);
+
+	WRITE_ONCE(iowq->hit_timeout, 1);
+	wake_up_process(iowq->wq.private);
+	return HRTIMER_NORESTART;
+}
+
+static int io_cqring_schedule_timeout(struct io_wait_queue *iowq,
+				      clockid_t clock_id)
+{
+	iowq->hit_timeout = 0;
+	hrtimer_init_on_stack(&iowq->t, clock_id, HRTIMER_MODE_ABS);
+	iowq->t.function = io_cqring_timer_wakeup;
+	hrtimer_set_expires_range_ns(&iowq->t, iowq->timeout, 0);
+	hrtimer_start_expires(&iowq->t, HRTIMER_MODE_ABS);
+
+	if (!READ_ONCE(iowq->hit_timeout))
+		schedule();
+
+	hrtimer_cancel(&iowq->t);
+	destroy_hrtimer_on_stack(&iowq->t);
+	__set_current_state(TASK_RUNNING);
+
+	return READ_ONCE(iowq->hit_timeout) ? -ETIME : 0;
+}
+
 static int __io_cqring_wait_schedule(struct io_ring_ctx *ctx,
 				     struct io_wait_queue *iowq)
 {
@@ -2362,11 +2390,10 @@ static int __io_cqring_wait_schedule(struct io_ring_ctx *ctx,
 	 */
 	if (current_pending_io())
 		current->in_iowait = 1;
-	if (iowq->timeout == KTIME_MAX)
+	if (iowq->timeout != KTIME_MAX)
+		ret = io_cqring_schedule_timeout(iowq, ctx->clockid);
+	else
 		schedule();
-	else if (!schedule_hrtimeout_range_clock(&iowq->timeout, 0,
-						 HRTIMER_MODE_ABS, ctx->clockid))
-		ret = -ETIME;
 	current->in_iowait = 0;
 	return ret;
 }

io_uring/io_uring.h

@@ -40,7 +40,9 @@ struct io_wait_queue {
 	struct io_ring_ctx *ctx;
 	unsigned cq_tail;
 	unsigned nr_timeouts;
+	int hit_timeout;
 	ktime_t timeout;
+	struct hrtimer t;
 
 #ifdef CONFIG_NET_RX_BUSY_POLL
 	ktime_t napi_busy_poll_dt;