From f25f776c9f9d6a0538cd9028d9d82fc6965d9123 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A9ter=20Szil=C3=A1gyi?= <peterke@gmail.com>
Date: Fri, 11 Jan 2019 15:27:47 +0200
Subject: core, light: get rid of the dual mutexes, hard to reason with

---
 light/lightchain.go      | 29 +++++++++++------------------
 light/lightchain_test.go |  4 ++--
 2 files changed, 13 insertions(+), 20 deletions(-)

(limited to 'light')

diff --git a/light/lightchain.go b/light/lightchain.go
index 8e2734c2d..de3d583c7 100644
--- a/light/lightchain.go
+++ b/light/lightchain.go
@@ -57,7 +57,6 @@ type LightChain struct {
 	scope         event.SubscriptionScope
 	genesisBlock  *types.Block
 
-	mu      sync.RWMutex
 	chainmu sync.RWMutex
 
 	bodyCache    *lru.Cache // Cache for the most recent block bodies
@@ -165,8 +164,8 @@ func (self *LightChain) loadLastState() error {
 // SetHead rewinds the local chain to a new head. Everything above the new
 // head will be deleted and the new one set.
 func (bc *LightChain) SetHead(head uint64) {
-	bc.mu.Lock()
-	defer bc.mu.Unlock()
+	bc.chainmu.Lock()
+	defer bc.chainmu.Unlock()
 
 	bc.hc.SetHead(head, nil)
 	bc.loadLastState()
@@ -188,8 +187,8 @@ func (bc *LightChain) ResetWithGenesisBlock(genesis *types.Block) {
 	// Dump the entire block chain and purge the caches
 	bc.SetHead(0)
 
-	bc.mu.Lock()
-	defer bc.mu.Unlock()
+	bc.chainmu.Lock()
+	defer bc.chainmu.Unlock()
 
 	// Prepare the genesis block and reinitialise the chain
 	rawdb.WriteTd(bc.chainDb, genesis.Hash(), genesis.NumberU64(), genesis.Difficulty())
@@ -315,8 +314,8 @@ func (bc *LightChain) Stop() {
 // Rollback is designed to remove a chain of links from the database that aren't
 // certain enough to be valid.
 func (self *LightChain) Rollback(chain []common.Hash) {
-	self.mu.Lock()
-	defer self.mu.Unlock()
+	self.chainmu.Lock()
+	defer self.chainmu.Unlock()
 
 	for i := len(chain) - 1; i >= 0; i-- {
 		hash := chain[i]
@@ -362,19 +361,13 @@ func (self *LightChain) InsertHeaderChain(chain []*types.Header, checkFreq int)
 
 	// Make sure only one thread manipulates the chain at once
 	self.chainmu.Lock()
-	defer func() {
-		self.chainmu.Unlock()
-		time.Sleep(time.Millisecond * 10) // ugly hack; do not hog chain lock in case syncing is CPU-limited by validation
-	}()
+	defer self.chainmu.Unlock()
 
 	self.wg.Add(1)
 	defer self.wg.Done()
 
 	var events []interface{}
 	whFunc := func(header *types.Header) error {
-		self.mu.Lock()
-		defer self.mu.Unlock()
-
 		status, err := self.hc.WriteHeader(header)
 
 		switch status {
@@ -441,8 +434,8 @@ func (self *LightChain) GetBlockHashesFromHash(hash common.Hash, max uint64) []c
 //
 // Note: ancestor == 0 returns the same block, 1 returns its parent and so on.
 func (bc *LightChain) GetAncestor(hash common.Hash, number, ancestor uint64, maxNonCanonical *uint64) (common.Hash, uint64) {
-	bc.chainmu.Lock()
-	defer bc.chainmu.Unlock()
+	bc.chainmu.RLock()
+	defer bc.chainmu.RUnlock()
 
 	return bc.hc.GetAncestor(hash, number, ancestor, maxNonCanonical)
 }
@@ -483,8 +476,8 @@ func (self *LightChain) SyncCht(ctx context.Context) bool {
 	}
 	// Retrieve the latest useful header and update to it
 	if header, err := GetHeaderByNumber(ctx, self.odr, latest); header != nil && err == nil {
-		self.mu.Lock()
-		defer self.mu.Unlock()
+		self.chainmu.Lock()
+		defer self.chainmu.Unlock()
 
 		// Ensure the chain didn't move past the latest block while retrieving it
 		if self.hc.CurrentHeader().Number.Uint64() < header.Number.Uint64() {
diff --git a/light/lightchain_test.go b/light/lightchain_test.go
index d45c0656d..374cb5319 100644
--- a/light/lightchain_test.go
+++ b/light/lightchain_test.go
@@ -122,10 +122,10 @@ func testHeaderChainImport(chain []*types.Header, lightchain *LightChain) error
 			return err
 		}
 		// Manually insert the header into the database, but don't reorganize (allows subsequent testing)
-		lightchain.mu.Lock()
+		lightchain.chainmu.Lock()
 		rawdb.WriteTd(lightchain.chainDb, header.Hash(), header.Number.Uint64(), new(big.Int).Add(header.Difficulty, lightchain.GetTdByHash(header.ParentHash)))
 		rawdb.WriteHeader(lightchain.chainDb, header)
-		lightchain.mu.Unlock()
+		lightchain.chainmu.Unlock()
 	}
 	return nil
 }
-- 
cgit v1.2.3