1 files changed, 69 insertions, 30 deletions
diff --git a/vendor/go.opentelemetry.io/otel/sdk/trace/provider.go b/vendor/go.opentelemetry.io/otel/sdk/trace/provider.go
index 201c17817..0a018c14d 100644
--- a/vendor/go.opentelemetry.io/otel/sdk/trace/provider.go
+++ b/vendor/go.opentelemetry.io/otel/sdk/trace/provider.go
@@ -75,8 +75,9 @@ func (cfg tracerProviderConfig) MarshalLog() interface{} {
 type TracerProvider struct {
 	mu             sync.Mutex
 	namedTracer    map[instrumentation.Scope]*tracer
-	spanProcessors atomic.Value
-	isShutdown     bool
+	spanProcessors atomic.Pointer[spanProcessorStates]
+
+	isShutdown atomic.Bool
 
 	// These fields are not protected by the lock mu. They are assumed to be
 	// immutable after creation of the TracerProvider.
@@ -119,11 +120,11 @@ func NewTracerProvider(opts ...TracerProviderOption) *TracerProvider {
 	}
 	global.Info("TracerProvider created", "config", o)
 
-	spss := spanProcessorStates{}
+	spss := make(spanProcessorStates, 0, len(o.processors))
 	for _, sp := range o.processors {
 		spss = append(spss, newSpanProcessorState(sp))
 	}
-	tp.spanProcessors.Store(spss)
+	tp.spanProcessors.Store(&spss)
 
 	return tp
 }
@@ -136,10 +137,11 @@ func NewTracerProvider(opts ...TracerProviderOption) *TracerProvider {
 //
 // This method is safe to be called concurrently.
 func (p *TracerProvider) Tracer(name string, opts ...trace.TracerOption) trace.Tracer {
+	// This check happens before the mutex is acquired to avoid deadlocking if Tracer() is called from within Shutdown().
+	if p.isShutdown.Load() {
+		return trace.NewNoopTracerProvider().Tracer(name, opts...)
+	}
 	c := trace.NewTracerConfig(opts...)
-
-	p.mu.Lock()
-	defer p.mu.Unlock()
 	if name == "" {
 		name = defaultTracerName
 	}
@@ -148,44 +150,74 @@ func (p *TracerProvider) Tracer(name string, opts ...trace.TracerOption) trace.T
 		Version:   c.InstrumentationVersion(),
 		SchemaURL: c.SchemaURL(),
 	}
-	t, ok := p.namedTracer[is]
-	if !ok {
-		t = &tracer{
-			provider:             p,
-			instrumentationScope: is,
+
+	t, ok := func() (trace.Tracer, bool) {
+		p.mu.Lock()
+		defer p.mu.Unlock()
+		// Must check the flag after acquiring the mutex to avoid returning a valid tracer if Shutdown() ran
+		// after the first check above but before we acquired the mutex.
+		if p.isShutdown.Load() {
+			return trace.NewNoopTracerProvider().Tracer(name, opts...), true
+		}
+		t, ok := p.namedTracer[is]
+		if !ok {
+			t = &tracer{
+				provider:             p,
+				instrumentationScope: is,
+			}
+			p.namedTracer[is] = t
 		}
-		p.namedTracer[is] = t
-		global.Info("Tracer created", "name", name, "version", c.InstrumentationVersion(), "schemaURL", c.SchemaURL())
+		return t, ok
+	}()
+	if !ok {
+		// This code is outside the mutex to not hold the lock while calling third party logging code:
+		// - That code may do slow things like I/O, which would prolong the duration the lock is held,
+		//   slowing down all tracing consumers.
+		// - Logging code may be instrumented with tracing and deadlock because it could try
+		//   acquiring the same non-reentrant mutex.
+		global.Info("Tracer created", "name", name, "version", is.Version, "schemaURL", is.SchemaURL)
 	}
 	return t
 }
 
 // RegisterSpanProcessor adds the given SpanProcessor to the list of SpanProcessors.
 func (p *TracerProvider) RegisterSpanProcessor(sp SpanProcessor) {
+	// This check prevents calls during a shutdown.
+	if p.isShutdown.Load() {
+		return
+	}
 	p.mu.Lock()
 	defer p.mu.Unlock()
-	if p.isShutdown {
+	// This check prevents calls after a shutdown.
+	if p.isShutdown.Load() {
 		return
 	}
-	newSPS := spanProcessorStates{}
-	newSPS = append(newSPS, p.spanProcessors.Load().(spanProcessorStates)...)
+
+	current := p.getSpanProcessors()
+	newSPS := make(spanProcessorStates, 0, len(current)+1)
+	newSPS = append(newSPS, current...)
 	newSPS = append(newSPS, newSpanProcessorState(sp))
-	p.spanProcessors.Store(newSPS)
+	p.spanProcessors.Store(&newSPS)
 }
 
 // UnregisterSpanProcessor removes the given SpanProcessor from the list of SpanProcessors.
 func (p *TracerProvider) UnregisterSpanProcessor(sp SpanProcessor) {
+	// This check prevents calls during a shutdown.
+	if p.isShutdown.Load() {
+		return
+	}
 	p.mu.Lock()
 	defer p.mu.Unlock()
-	if p.isShutdown {
+	// This check prevents calls after a shutdown.
+	if p.isShutdown.Load() {
 		return
 	}
-	old := p.spanProcessors.Load().(spanProcessorStates)
+	old := p.getSpanProcessors()
 	if len(old) == 0 {
 		return
 	}
-	spss := spanProcessorStates{}
-	spss = append(spss, old...)
+	spss := make(spanProcessorStates, len(old))
+	copy(spss, old)
 
 	// stop the span processor if it is started and remove it from the list
 	var stopOnce *spanProcessorState
@@ -209,13 +241,13 @@ func (p *TracerProvider) UnregisterSpanProcessor(sp SpanProcessor) {
 	spss[len(spss)-1] = nil
 	spss = spss[:len(spss)-1]
 
-	p.spanProcessors.Store(spss)
+	p.spanProcessors.Store(&spss)
 }
 
 // ForceFlush immediately exports all spans that have not yet been exported for
 // all the registered span processors.
 func (p *TracerProvider) ForceFlush(ctx context.Context) error {
-	spss := p.spanProcessors.Load().(spanProcessorStates)
+	spss := p.getSpanProcessors()
 	if len(spss) == 0 {
 		return nil
 	}
@@ -236,18 +268,21 @@ func (p *TracerProvider) ForceFlush(ctx context.Context) error {
 
 // Shutdown shuts down TracerProvider. All registered span processors are shut down
 // in the order they were registered and any held computational resources are released.
+// After Shutdown is called, all methods are no-ops.
 func (p *TracerProvider) Shutdown(ctx context.Context) error {
-	spss := p.spanProcessors.Load().(spanProcessorStates)
-	if len(spss) == 0 {
+	// This check prevents deadlocks in case of recursive shutdown.
+	if p.isShutdown.Load() {
 		return nil
 	}
-
 	p.mu.Lock()
 	defer p.mu.Unlock()
-	p.isShutdown = true
+	// This check prevents calls after a shutdown has already been done concurrently.
+	if !p.isShutdown.CompareAndSwap(false, true) { // did toggle?
+		return nil
+	}
 
 	var retErr error
-	for _, sps := range spss {
+	for _, sps := range p.getSpanProcessors() {
 		select {
 		case <-ctx.Done():
 			return ctx.Err()
@@ -267,10 +302,14 @@ func (p *TracerProvider) Shutdown(ctx context.Context) error {
 			}
 		}
 	}
-	p.spanProcessors.Store(spanProcessorStates{})
+	p.spanProcessors.Store(&spanProcessorStates{})
 	return retErr
 }
 
+func (p *TracerProvider) getSpanProcessors() spanProcessorStates {
+	return *(p.spanProcessors.Load())
+}
+
 // TracerProviderOption configures a TracerProvider.
 type TracerProviderOption interface {
 	apply(tracerProviderConfig) tracerProviderConfig