Fix MpoolLocker

Signed-off-by: Jakub Sztandera <kubuxu@protocol.ai>

node/modules/dtypes/mpool.go

@@ -0,0 +1,35 @@
+package dtypes
+
+import (
+	"context"
+	"sync"
+
+	"github.com/filecoin-project/go-address"
+)
+
+type MpoolLocker struct {
+	m  map[address.Address]chan struct{}
+	lk sync.Mutex
+}
+
+func (ml *MpoolLocker) TakeLock(ctx context.Context, a address.Address) (func(), error) {
+	ml.lk.Lock()
+	if ml.m == nil {
+		ml.m = make(map[address.Address]chan struct{})
+	}
+	lk, ok := ml.m[a]
+	if !ok {
+		lk = make(chan struct{}, 1)
+		ml.m[a] = lk
+	}
+	ml.lk.Unlock()
+
+	select {
+	case lk <- struct{}{}:
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	}
+	return func() {
+		<-lk
+	}, nil
+}