[#1700] shard: Lock shard's mode mutex on close

To prevent race between GC handlers and close.

Change-Id: I06219230964f000f666a56158d3563c760518c3b
Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

pkg/local_object_storage/shard/control.go

@@ -363,6 +363,7 @@ func (s *Shard) refillTombstoneObject(ctx context.Context, obj *objectSDK.Object
 
 // Close releases all Shard's components.
 func (s *Shard) Close(ctx context.Context) error {
+	unlock := s.lockExclusive()
 	if s.rb != nil {
 		s.rb.Stop(ctx, s.log)
 	}
@@ -388,15 +389,19 @@ func (s *Shard) Close(ctx context.Context) error {
 		}
 	}
 
+	if s.opsLimiter != nil {
+		s.opsLimiter.Close()
+	}
+
+	unlock()
+
+	// GC waits for handlers and remover to complete. Handlers may try to lock shard's lock.
+	// So to prevent deadlock GC stopping is outside of exclusive lock.
 	// If Init/Open was unsuccessful gc can be nil.
 	if s.gc != nil {
 		s.gc.stop(ctx)
 	}
 
-	if s.opsLimiter != nil {
-		s.opsLimiter.Close()
-	}
-
 	return lastErr
 }