diff --git a/include/core/SkPixelRef.h b/include/core/SkPixelRef.h
index 49f0f97..52e679e 100644
--- a/include/core/SkPixelRef.h
+++ b/include/core/SkPixelRef.h
@@ -88,7 +88,7 @@
         virtual void onChange() = 0;
     };
 
-    // Takes ownership of listener.
+    // Takes ownership of listener.  Threadsafe.
     void addGenIDChangeListener(GenIDChangeListener* listener);
 
     // Call when this pixelref is part of the key to a resourcecache entry. This allows the cache
@@ -119,6 +119,7 @@
     const uint32_t fStableID;
 #endif
 
+    SkMutex                         fGenIDChangeListenersMutex;
     SkTDArray<GenIDChangeListener*> fGenIDChangeListeners;  // pointers are owned
 
     // Set true by caches when they cache content that's derived from the current pixels.
diff --git a/include/private/SkPathRef.h b/include/private/SkPathRef.h
index b9b52d4..0a1c579 100644
--- a/include/private/SkPathRef.h
+++ b/include/private/SkPathRef.h
@@ -12,6 +12,7 @@
 #include "../private/SkAtomics.h"
 #include "../private/SkTDArray.h"
 #include "SkMatrix.h"
+#include "SkMutex.h"
 #include "SkPoint.h"
 #include "SkRRect.h"
 #include "SkRect.h"
@@ -311,7 +312,7 @@
         virtual void onChange() = 0;
     };
 
-    void addGenIDChangeListener(GenIDChangeListener* listener);
+    void addGenIDChangeListener(GenIDChangeListener* listener);  // Threadsafe
 
     bool isValid() const;
     SkDEBUGCODE(void validate() const { SkASSERT(this->isValid()); } )
@@ -538,6 +539,7 @@
     mutable uint32_t    fGenerationID;
     SkDEBUGCODE(int32_t fEditorsAttached;) // assert that only one editor in use at any time.
 
+    SkMutex                         fGenIDChangeListenersMutex;
     SkTDArray<GenIDChangeListener*> fGenIDChangeListeners;  // pointers are owned
 
     mutable uint8_t  fBoundsIsDirty;
diff --git a/src/core/SkPathRef.cpp b/src/core/SkPathRef.cpp
index c710f71..a725f7e 100644
--- a/src/core/SkPathRef.cpp
+++ b/src/core/SkPathRef.cpp
@@ -670,11 +670,13 @@
         delete listener;
         return;
     }
+    SkAutoMutexAcquire lock(fGenIDChangeListenersMutex);
     *fGenIDChangeListeners.append() = listener;
 }
 
 // we need to be called *before* the genID gets changed or zerod
 void SkPathRef::callGenIDChangeListeners() {
+    SkAutoMutexAcquire lock(fGenIDChangeListenersMutex);
     for (int i = 0; i < fGenIDChangeListeners.count(); i++) {
         fGenIDChangeListeners[i]->onChange();
     }
diff --git a/src/core/SkPixelRef.cpp b/src/core/SkPixelRef.cpp
index d5e9360..868ac8c 100644
--- a/src/core/SkPixelRef.cpp
+++ b/src/core/SkPixelRef.cpp
@@ -92,11 +92,13 @@
         delete listener;
         return;
     }
+    SkAutoMutexAcquire lock(fGenIDChangeListenersMutex);
     *fGenIDChangeListeners.append() = listener;
 }
 
 // we need to be called *before* the genID gets changed or zerod
 void SkPixelRef::callGenIDChangeListeners() {
+    SkAutoMutexAcquire lock(fGenIDChangeListenersMutex);
     // We don't invalidate ourselves if we think another SkPixelRef is sharing our genID.
     if (this->genIDIsUnique()) {
         for (int i = 0; i < fGenIDChangeListeners.count(); i++) {