From 5f799922a84795a7dbd5c0577bc3c3e6e42baaf5 Mon Sep 17 00:00:00 2001
From: tangcong <tangcong506@gmail.com>
Date: Sun, 26 Apr 2020 21:05:30 +0800
Subject: [PATCH] mvcc: fix deadlock bug

---
 mvcc/kvstore.go | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/mvcc/kvstore.go b/mvcc/kvstore.go
index ba34cd1f314..2a8a0361a0b 100644
--- a/mvcc/kvstore.go
+++ b/mvcc/kvstore.go
@@ -142,14 +142,18 @@ func NewStore(b backend.Backend, le lease.Lessor, ig ConsistentIndexGetter) *sto
 
 func (s *store) compactBarrier(ctx context.Context, ch chan struct{}) {
 	if ctx == nil || ctx.Err() != nil {
-		s.mu.Lock()
 		select {
 		case <-s.stopc:
 		default:
+			// fix deadlock in mvcc,for more information, please refer to pr 11817.
+			// s.stopc is only updated in restore operation, which is called by apply
+			// snapshot call, compaction and apply snapshot requests are serialized by
+			// raft, and do not happen at the same time.
+			s.mu.Lock()
 			f := func(ctx context.Context) { s.compactBarrier(ctx, ch) }
 			s.fifoSched.Schedule(f)
+			s.mu.Unlock()
 		}
-		s.mu.Unlock()
 		return
 	}
 	close(ch)