Bug 832609 - Make memory reporter for blobs threadsafe. r=khuey

--HG--
extra : rebase_source : 4dc2387ae3867699085139545ff2b57104b1f72a

content/base/public/nsDOMFile.h

@@ -22,6 +22,7 @@
 #include "mozilla/GuardObjects.h"
 #include "mozilla/LinkedList.h"
 #include "mozilla/StandardInteger.h"
+#include "mozilla/StaticMutex.h"
 #include "mozilla/StaticPtr.h"
 #include "mozilla/dom/DOMError.h"
 #include "mozilla/dom/indexedDB/FileInfo.h"
@@ -343,6 +344,10 @@ protected:
   bool mStoredFile;
 };
 
+/**
+ * This class may be used off the main thread, and in particular, its
+ * constructor and destructor may not run on the same thread.  Be careful!
+ */
 class nsDOMMemoryFile : public nsDOMFile
 {
 public:
@@ -394,6 +399,8 @@ protected:
       : mData(aMemoryBuffer)
       , mLength(aLength)
     {
+      mozilla::StaticMutexAutoLock lock(sDataOwnerMutex);
+
       if (!sDataOwners) {
         sDataOwners = new mozilla::LinkedList<DataOwner>();
         EnsureMemoryReporterRegistered();
@@ -402,6 +409,8 @@ protected:
     }
 
     ~DataOwner() {
+      mozilla::StaticMutexAutoLock lock(sDataOwnerMutex);
+
       remove();
       if (sDataOwners->isEmpty()) {
         // Free the linked list if it's empty.
@@ -413,8 +422,13 @@ protected:
 
     static void EnsureMemoryReporterRegistered();
 
-    static bool sMemoryReporterRegistered;
+    // sDataOwners and sMemoryReporterRegistered may only be accessed while
+    // holding sDataOwnerMutex!  You also must hold the mutex while touching
+    // elements of the linked list that DataOwner inherits from.
+    static mozilla::StaticMutex sDataOwnerMutex;
     static mozilla::StaticAutoPtr<mozilla::LinkedList<DataOwner> > sDataOwners;
+    static bool sMemoryReporterRegistered;
+
     void* mData;
     uint64_t mLength;
   };

content/base/src/nsDOMFile.cpp

@@ -611,6 +611,9 @@ nsDOMMemoryFile::GetInternalStream(nsIInputStream **aStream)
   return DataOwnerAdapter::Create(mDataOwner, mStart, mLength, aStream);
 }
 
+/* static */ StaticMutex
+nsDOMMemoryFile::DataOwner::sDataOwnerMutex;
+
 /* static */ StaticAutoPtr<LinkedList<nsDOMMemoryFile::DataOwner> >
 nsDOMMemoryFile::DataOwner::sDataOwners;
 
@@ -635,6 +638,8 @@ class nsDOMMemoryFileDataOwnerMemoryReporter MOZ_FINAL
   {
     typedef nsDOMMemoryFile::DataOwner DataOwner;
 
+    StaticMutexAutoLock lock(DataOwner::sDataOwnerMutex);
+
     if (!DataOwner::sDataOwners) {
       return NS_OK;
     }