Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

	sm.schedulerWG.RunWithLog(func() {
		defer func() {
			scheduler.Close()
			sm.delScheduler(task.ID)
			if allocateSlots {
				sm.slotMgr.unReserve(basicTask, reservedExecID)
			}
			handle.NotifyTaskChange()
			sm.logger.Info("task scheduler exit", zap.Int64("task-id", task.ID))
		}()
		metrics.UpdateMetricsForRunTask(task)
		scheduler.ScheduleTask()
		sm.finishCh <- struct{}{}
	})

finishCh may be blocked. If more than 2x concurrency tasks are put into finishCh and it still can handle any result. New task would be blocked because no slot is available.

2. What did you expect to see? (Required)

N/A

3. What did you see instead (Required)

N/A

4. What is your TiDB version? (Required)

master