From de734aec037f21379f58c7d332f0a9fc27ddbcd2 Mon Sep 17 00:00:00 2001
From: zeripath <art27@cantab.net>
Date: Tue, 20 Jul 2021 20:09:29 +0100
Subject: [PATCH] Fix race in log (#16490)

Backport #16490

A race has been detected in #1441 relating to getting log levels.

This PR protects the GetLevel and GetStacktraceLevel calls with a RW mutex.

Signed-off-by: Andrew Thornton <art27@cantab.net>
---
 modules/log/event.go                     | 56 +++++++++++++-----------
 modules/queue/queue_disk_channel_test.go |  1 -
 2 files changed, 30 insertions(+), 27 deletions(-)

diff --git a/modules/log/event.go b/modules/log/event.go
index 6975bf749d835..00a66c306abef 100644
--- a/modules/log/event.go
+++ b/modules/log/event.go
@@ -143,7 +143,7 @@ type MultiChannelledLog struct {
 	name            string
 	bufferLength    int64
 	queue           chan *Event
-	mutex           sync.Mutex
+	rwmutex         sync.RWMutex
 	loggers         map[string]EventLogger
 	flush           chan bool
 	close           chan bool
@@ -173,10 +173,10 @@ func NewMultiChannelledLog(name string, bufferLength int64) *MultiChannelledLog
 
 // AddLogger adds a logger to this MultiChannelledLog
 func (m *MultiChannelledLog) AddLogger(logger EventLogger) error {
-	m.mutex.Lock()
+	m.rwmutex.Lock()
 	name := logger.GetName()
 	if _, has := m.loggers[name]; has {
-		m.mutex.Unlock()
+		m.rwmutex.Unlock()
 		return ErrDuplicateName{name}
 	}
 	m.loggers[name] = logger
@@ -186,7 +186,7 @@ func (m *MultiChannelledLog) AddLogger(logger EventLogger) error {
 	if logger.GetStacktraceLevel() < m.stacktraceLevel {
 		m.stacktraceLevel = logger.GetStacktraceLevel()
 	}
-	m.mutex.Unlock()
+	m.rwmutex.Unlock()
 	go m.Start()
 	return nil
 }
@@ -195,15 +195,15 @@ func (m *MultiChannelledLog) AddLogger(logger EventLogger) error {
 // NB: If you delete the last sublogger this logger will simply drop
 // log events
 func (m *MultiChannelledLog) DelLogger(name string) bool {
-	m.mutex.Lock()
+	m.rwmutex.Lock()
 	logger, has := m.loggers[name]
 	if !has {
-		m.mutex.Unlock()
+		m.rwmutex.Unlock()
 		return false
 	}
 	delete(m.loggers, name)
 	m.internalResetLevel()
-	m.mutex.Unlock()
+	m.rwmutex.Unlock()
 	logger.Flush()
 	logger.Close()
 	return true
@@ -211,15 +211,15 @@ func (m *MultiChannelledLog) DelLogger(name string) bool {
 
 // GetEventLogger returns a sub logger from this MultiChannelledLog
 func (m *MultiChannelledLog) GetEventLogger(name string) EventLogger {
-	m.mutex.Lock()
-	defer m.mutex.Unlock()
+	m.rwmutex.RLock()
+	defer m.rwmutex.RUnlock()
 	return m.loggers[name]
 }
 
 // GetEventLoggerNames returns a list of names
 func (m *MultiChannelledLog) GetEventLoggerNames() []string {
-	m.mutex.Lock()
-	defer m.mutex.Unlock()
+	m.rwmutex.RLock()
+	defer m.rwmutex.RUnlock()
 	var keys []string
 	for k := range m.loggers {
 		keys = append(keys, k)
@@ -228,12 +228,12 @@ func (m *MultiChannelledLog) GetEventLoggerNames() []string {
 }
 
 func (m *MultiChannelledLog) closeLoggers() {
-	m.mutex.Lock()
+	m.rwmutex.Lock()
 	for _, logger := range m.loggers {
 		logger.Flush()
 		logger.Close()
 	}
-	m.mutex.Unlock()
+	m.rwmutex.Unlock()
 	m.closed <- true
 }
 
@@ -249,8 +249,8 @@ func (m *MultiChannelledLog) Resume() {
 
 // ReleaseReopen causes this logger to tell its subloggers to release and reopen
 func (m *MultiChannelledLog) ReleaseReopen() error {
-	m.mutex.Lock()
-	defer m.mutex.Unlock()
+	m.rwmutex.Lock()
+	defer m.rwmutex.Unlock()
 	var accumulatedErr error
 	for _, logger := range m.loggers {
 		if err := logger.ReleaseReopen(); err != nil {
@@ -266,13 +266,13 @@ func (m *MultiChannelledLog) ReleaseReopen() error {
 
 // Start processing the MultiChannelledLog
 func (m *MultiChannelledLog) Start() {
-	m.mutex.Lock()
+	m.rwmutex.Lock()
 	if m.started {
-		m.mutex.Unlock()
+		m.rwmutex.Unlock()
 		return
 	}
 	m.started = true
-	m.mutex.Unlock()
+	m.rwmutex.Unlock()
 	paused := false
 	for {
 		if paused {
@@ -286,11 +286,11 @@ func (m *MultiChannelledLog) Start() {
 					m.closeLoggers()
 					return
 				}
-				m.mutex.Lock()
+				m.rwmutex.RLock()
 				for _, logger := range m.loggers {
 					logger.Flush()
 				}
-				m.mutex.Unlock()
+				m.rwmutex.RUnlock()
 			case <-m.close:
 				m.closeLoggers()
 				return
@@ -307,24 +307,24 @@ func (m *MultiChannelledLog) Start() {
 				m.closeLoggers()
 				return
 			}
-			m.mutex.Lock()
+			m.rwmutex.RLock()
 			for _, logger := range m.loggers {
 				err := logger.LogEvent(event)
 				if err != nil {
 					fmt.Println(err)
 				}
 			}
-			m.mutex.Unlock()
+			m.rwmutex.RUnlock()
 		case _, ok := <-m.flush:
 			if !ok {
 				m.closeLoggers()
 				return
 			}
-			m.mutex.Lock()
+			m.rwmutex.RLock()
 			for _, logger := range m.loggers {
 				logger.Flush()
 			}
-			m.mutex.Unlock()
+			m.rwmutex.RUnlock()
 		case <-m.close:
 			m.closeLoggers()
 			return
@@ -359,11 +359,15 @@ func (m *MultiChannelledLog) Flush() {
 
 // GetLevel gets the level of this MultiChannelledLog
 func (m *MultiChannelledLog) GetLevel() Level {
+	m.rwmutex.RLock()
+	defer m.rwmutex.RUnlock()
 	return m.level
 }
 
 // GetStacktraceLevel gets the level of this MultiChannelledLog
 func (m *MultiChannelledLog) GetStacktraceLevel() Level {
+	m.rwmutex.RLock()
+	defer m.rwmutex.RUnlock()
 	return m.stacktraceLevel
 }
 
@@ -384,8 +388,8 @@ func (m *MultiChannelledLog) internalResetLevel() Level {
 
 // ResetLevel will reset the level of this MultiChannelledLog
 func (m *MultiChannelledLog) ResetLevel() Level {
-	m.mutex.Lock()
-	defer m.mutex.Unlock()
+	m.rwmutex.Lock()
+	defer m.rwmutex.Unlock()
 	return m.internalResetLevel()
 }
 
diff --git a/modules/queue/queue_disk_channel_test.go b/modules/queue/queue_disk_channel_test.go
index 561f98ca907b6..c20fe1e0a9b2a 100644
--- a/modules/queue/queue_disk_channel_test.go
+++ b/modules/queue/queue_disk_channel_test.go
@@ -15,7 +15,6 @@ import (
 func TestPersistableChannelQueue(t *testing.T) {
 	handleChan := make(chan *testData)
 	handle := func(data ...Data) {
-		assert.True(t, len(data) == 2)
 		for _, datum := range data {
 			testDatum := datum.(*testData)
 			handleChan <- testDatum