Global logger uses an atomic value instead of a mutex.

Signed-off-by: Bogdan Drutu <bogdandrutu@gmail.com>

CHANGELOG.md

@@ -16,6 +16,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 - Add `Producer` interface and `Reader.RegisterProducer(Producer)` to `go.opentelemetry.io/otel/sdk/metric` to enable external metric Producers. (#3524)
 
+### Changed
+
+- Global logger uses an atomic value instead of a mutex. (#3545)
+
 ## [1.11.2/0.34.0] 2022-12-05
 
 ### Added

internal/global/internal_logging.go

@@ -17,7 +17,7 @@ package global // import "go.opentelemetry.io/otel/internal/global"
 import (
 	"log"
 	"os"
-	"sync"
+	"sync/atomic"
 
 	"github.com/go-logr/logr"
 	"github.com/go-logr/stdr"
@@ -27,37 +27,36 @@ import (
 //
 // The default logger uses stdr which is backed by the standard `log.Logger`
 // interface. This logger will only show messages at the Error Level.
-var globalLogger logr.Logger = stdr.New(log.New(os.Stderr, "", log.LstdFlags|log.Lshortfile))
-var globalLoggerLock = &sync.RWMutex{}
+var globalLogger = func() *atomic.Value {
+	dl := &atomic.Value{}
+	dl.Store(stdr.New(log.New(os.Stderr, "", log.LstdFlags|log.Lshortfile)))
+	return dl
+}()
 
 // SetLogger overrides the globalLogger with l.
 //
 // To see Info messages use a logger with `l.V(1).Enabled() == true`
 // To see Debug messages use a logger with `l.V(5).Enabled() == true`.
 func SetLogger(l logr.Logger) {
-	globalLoggerLock.Lock()
-	defer globalLoggerLock.Unlock()
-	globalLogger = l
+	globalLogger.Store(l)
+}
+
+func getLogger() logr.Logger {
+	return globalLogger.Load().(logr.Logger)
 }
 
 // Info prints messages about the general state of the API or SDK.
 // This should usually be less then 5 messages a minute.
 func Info(msg string, keysAndValues ...interface{}) {
-	globalLoggerLock.RLock()
-	defer globalLoggerLock.RUnlock()
-	globalLogger.V(1).Info(msg, keysAndValues...)
+	getLogger().V(1).Info(msg, keysAndValues...)
 }
 
 // Error prints messages about exceptional states of the API or SDK.
 func Error(err error, msg string, keysAndValues ...interface{}) {
-	globalLoggerLock.RLock()
-	defer globalLoggerLock.RUnlock()
-	globalLogger.Error(err, msg, keysAndValues...)
+	getLogger().Error(err, msg, keysAndValues...)
 }
 
 // Debug prints messages about all internal changes in the API or SDK.
 func Debug(msg string, keysAndValues ...interface{}) {
-	globalLoggerLock.RLock()
-	defer globalLoggerLock.RUnlock()
-	globalLogger.V(5).Info(msg, keysAndValues...)
+	getLogger().V(5).Info(msg, keysAndValues...)
 }