sched_worker.go has dead lock

[gavin-ygy]

Describe the bug
if the miner can't add new worker anymore.

Version (run lotus version):
v1.4.0
Additional context
sector-storage/sched_worker.go
func (sh *scheduler) runWorker(ctx context.Context, w Worker) error {
info, err := w.Info(ctx)
if err != nil {
return xerrors.Errorf("getting worker info: %w", err)
}

sessID, err := w.Session(ctx)
if err != nil {
	return xerrors.Errorf("getting worker session: %w", err)
}
if sessID == ClosedWorkerID {
	return xerrors.Errorf("worker already closed")
}

worker := &workerHandle{
	workerRpc: w,
	info:      info,

	preparing: &activeResources{},
	active:    &activeResources{},
	enabled:   true,

	closingMgr: make(chan struct{}),
	closedMgr:  make(chan struct{}),
}

wid := WorkerID(sessID)

sh.workersLk.Lock()
_, exist := sh.workers[wid]
if exist {
	log.Warnw("duplicated worker added", "id", wid)

	sh.workersLk.Unlock()  //****************Gavin adding this line and fix the bug!

	// this is ok, we're already handling this worker in a different goroutine
	return nil
}
   sh.workers[wid] = worker
sh.workersLk.Unlock()

//...
}

[magik6k]

Good catch! Fixed in #5251