Follow up #16068 (comment)

Replace unnecessary Lock()/Unlock()s with RLock()/RUnlock()s

Signed-off-by: caojiamingalan <[email protected]>

server/storage/backend/read_tx.go

@@ -26,8 +26,13 @@ import (
 // is known to never overwrite any key so range is safe.
 
 type ReadTx interface {
+	// Lock and Unlock should only be used in the following three cases:
+	// 1. When committing a transaction. Because it will reset the read tx, including the buffer;
+	// 2. When writing the pending data back to read buf, because obviously no reading is allowed when writing the read buffer;
+	// 3. When performing defragmentation, because again it will reset the read tx, including the read buffer.
 	Lock()
 	Unlock()
+	// RLock and RUnlock should be used for all other cases.
 	RLock()
 	RUnlock()
 

server/storage/mvcc/kvstore.go

@@ -228,8 +228,8 @@ func (s *store) updateCompactRev(rev int64) (<-chan struct{}, int64, error) {
 // checkPrevCompactionCompleted checks whether the previous scheduled compaction is completed.
 func (s *store) checkPrevCompactionCompleted() bool {
 	tx := s.b.ReadTx()
-	tx.Lock()
-	defer tx.Unlock()
+	tx.RLock()
+	defer tx.RUnlock()
 	scheduledCompact, scheduledCompactFound := UnsafeReadScheduledCompact(tx)
 	finishedCompact, finishedCompactFound := UnsafeReadFinishedCompact(tx)
 	return scheduledCompact == finishedCompact && scheduledCompactFound == finishedCompactFound
@@ -328,7 +328,7 @@ func (s *store) restore() error {
 
 	// restore index
 	tx := s.b.ReadTx()
-	tx.Lock()
+	tx.RLock()
 
 	finishedCompact, found := UnsafeReadFinishedCompact(tx)
 	if found {
@@ -384,7 +384,7 @@ func (s *store) restore() error {
 
 	for key, lid := range keyToLease {
 		if s.le == nil {
-			tx.Unlock()
+			tx.RUnlock()
 			panic("no lessor to attach lease")
 		}
 		err := s.le.Attach(lid, []lease.LeaseItem{{Key: key}})
@@ -397,7 +397,7 @@ func (s *store) restore() error {
 		}
 	}
 
-	tx.Unlock()
+	tx.RUnlock()
 
 	s.lg.Info("kvstore restored", zap.Int64("current-rev", s.currentRev))
 

server/storage/schema/alarm.go

@@ -74,8 +74,8 @@ func (s *alarmBackend) mustUnsafeDeleteAlarm(tx backend.BatchTx, alarm *etcdserv
 
 func (s *alarmBackend) GetAllAlarms() ([]*etcdserverpb.AlarmMember, error) {
 	tx := s.be.ReadTx()
-	tx.Lock()
-	defer tx.Unlock()
+	tx.RLock()
+	defer tx.RUnlock()
 	return s.unsafeGetAllAlarms(tx)
 }
 

server/storage/schema/membership.go

@@ -207,8 +207,8 @@ func (s *membershipBackend) ClusterVersionFromBackend() *semver.Version {
 func (s *membershipBackend) DowngradeInfoFromBackend() *version.DowngradeInfo {
 	dkey := ClusterDowngradeKeyName
 	tx := s.be.ReadTx()
-	tx.Lock()
-	defer tx.Unlock()
+	tx.RLock()
+	defer tx.RUnlock()
 	keys, vals := tx.UnsafeRange(Cluster, dkey, nil, 0)
 	if len(keys) == 0 {
 		return nil

server/storage/schema/schema.go

@@ -27,8 +27,8 @@ import (
 
 // Validate checks provided backend to confirm that schema used is supported.
 func Validate(lg *zap.Logger, tx backend.ReadTx) error {
-	tx.Lock()
-	defer tx.Unlock()
+	tx.RLock()
+	defer tx.RUnlock()
 	return unsafeValidate(lg, tx)
 }
 

server/storage/schema/version.go

@@ -24,8 +24,8 @@ import (
 // ReadStorageVersion loads storage version from given backend transaction.
 // Populated since v3.6
 func ReadStorageVersion(tx backend.ReadTx) *semver.Version {
-	tx.Lock()
-	defer tx.Unlock()
+	tx.RLock()
+	defer tx.RUnlock()
 	return UnsafeReadStorageVersion(tx)
 }