all: replace RWMutex with Mutex in places where RLock is not used (#21622)

accounts/keystore/file_cache.go

@@ -31,7 +31,7 @@ import (
 type fileCache struct {
 	all     mapset.Set // Set of all files from the keystore folder
 	lastMod time.Time  // Last time instance when a file was modified
-	mu      sync.RWMutex
+	mu      sync.Mutex
 }
 
 // scan performs a new scan on the given directory, compares against the already

core/chain_indexer.go

@@ -86,7 +86,7 @@ type ChainIndexer struct {
 	throttling time.Duration // Disk throttling to prevent a heavy upgrade from hogging resources
 
 	log  log.Logger
-	lock sync.RWMutex
+	lock sync.Mutex
 }
 
 // NewChainIndexer creates a new chain indexer to do background processing on

eth/downloader/downloader.go

@@ -145,7 +145,7 @@ type Downloader struct {
 	cancelLock sync.RWMutex  // Lock to protect the cancel channel and peer in delivers
 
 	quitCh   chan struct{} // Quit channel to signal termination
-	quitLock sync.RWMutex  // Lock to prevent double closes
+	quitLock sync.Mutex    // Lock to prevent double closes
 
 	// Testing hooks
 	syncInitHook     func(uint64, uint64)  // Method to call upon initiating a new sync run

les/txrelay.go

@@ -34,7 +34,7 @@ type LesTxRelay struct {
 	ps           *peerSet
 	peerList     []*peer
 	peerStartPos int
-	lock         sync.RWMutex
+	lock         sync.Mutex
 
 	reqDist *requestDistributor
 }

miner/unconfirmed.go

@@ -47,7 +47,7 @@ type unconfirmedBlocks struct {
 	chain  headerRetriever // Blockchain to verify canonical status through
 	depth  uint            // Depth after which to discard previous blocks
 	blocks *ring.Ring      // Block infos to allow canonical chain cross checks
-	lock   sync.RWMutex    // Protects the fields from concurrent access
+	lock   sync.Mutex      // Protects the fields from concurrent access
 }
 
 // newUnconfirmedBlocks returns new data structure to track currently unconfirmed blocks.