Bug 684887 part B - make a SafeMutex which should crash if you try to recursively lock it, instead of deadlocking. r=bent

--HG--
extra : rebase_source : 694c5cd571e5802ce5e5af4ea03b9edc7e6fb8d4

xpcom/components/nsComponentManager.cpp

@@ -203,7 +203,7 @@ namespace {
 class NS_STACK_CLASS MutexLock
 {
 public:
-    MutexLock(Mutex& aMutex)
+    MutexLock(SafeMutex& aMutex)
         : mMutex(aMutex)
         , mLocked(false)
     {
@@ -231,7 +231,7 @@ public:
     }
 
 private:
-    Mutex& mMutex;
+    SafeMutex& mMutex;
     bool mLocked;
 };
 
@@ -852,7 +852,7 @@ nsFactoryEntry *
 nsComponentManagerImpl::GetFactoryEntry(const char *aContractID,
                                         uint32_t aContractIDLen)
 {
-    MutexAutoLock lock(mLock);
+    SafeMutexAutoLock lock(mLock);
     return mContractIDs.Get(nsDependentCString(aContractID, aContractIDLen));
 }
 
@@ -860,7 +860,7 @@ nsComponentManagerImpl::GetFactoryEntry(const char *aContractID,
 nsFactoryEntry *
 nsComponentManagerImpl::GetFactoryEntry(const nsCID &aClass)
 {
-    MutexAutoLock lock(mLock);
+    SafeMutexAutoLock lock(mLock);
     return mFactories.Get(aClass);
 }
 
@@ -1220,7 +1220,7 @@ nsComponentManagerImpl::GetService(const nsCID& aClass,
         }
 
 
-        MutexAutoUnlock unlockPending(mLock);
+        SafeMutexAutoUnlock unlockPending(mLock);
 
         if (!currentThread) {
             currentThread = NS_GetCurrentThread();
@@ -1253,7 +1253,7 @@ nsComponentManagerImpl::GetService(const nsCID& aClass,
 
     nsresult rv;
     {
-        MutexAutoUnlock unlock(mLock);
+        SafeMutexAutoUnlock unlock(mLock);
         rv = CreateInstance(aClass, nullptr, aIID, getter_AddRefs(service));
     }
     if (NS_SUCCEEDED(rv) && !service) {
@@ -1310,7 +1310,7 @@ nsComponentManagerImpl::IsServiceInstantiated(const nsCID & aClass,
     nsFactoryEntry* entry;
 
     {
-        MutexAutoLock lock(mLock);
+        SafeMutexAutoLock lock(mLock);
         entry = mFactories.Get(aClass);
     }
 
@@ -1347,7 +1347,7 @@ NS_IMETHODIMP nsComponentManagerImpl::IsServiceInstantiatedByContractID(const ch
     nsresult rv = NS_ERROR_SERVICE_NOT_AVAILABLE;
     nsFactoryEntry *entry;
     {
-        MutexAutoLock lock(mLock);
+        SafeMutexAutoLock lock(mLock);
         entry = mContractIDs.Get(nsDependentCString(aContractID));
     }
 
@@ -1412,7 +1412,7 @@ nsComponentManagerImpl::GetServiceByContractID(const char* aContractID,
             return NS_ERROR_NOT_AVAILABLE;
         }
 
-        MutexAutoUnlock unlockPending(mLock);
+        SafeMutexAutoUnlock unlockPending(mLock);
 
         if (!currentThread) {
             currentThread = NS_GetCurrentThread();
@@ -1445,7 +1445,7 @@ nsComponentManagerImpl::GetServiceByContractID(const char* aContractID,
 
     nsresult rv;
     {
-        MutexAutoUnlock unlock(mLock);
+        SafeMutexAutoUnlock unlock(mLock);
         rv = CreateInstanceByContractID(aContractID, nullptr, aIID,
                                         getter_AddRefs(service));
     }
@@ -1505,7 +1505,7 @@ nsComponentManagerImpl::RegisterFactory(const nsCID& aClass,
         if (!aContractID)
             return NS_ERROR_INVALID_ARG;
 
-        MutexAutoLock lock(mLock);
+        SafeMutexAutoLock lock(mLock);
         nsFactoryEntry* oldf = mFactories.Get(aClass);
         if (!oldf)
             return NS_ERROR_FACTORY_NOT_REGISTERED;
@@ -1516,7 +1516,7 @@ nsComponentManagerImpl::RegisterFactory(const nsCID& aClass,
 
     nsAutoPtr<nsFactoryEntry> f(new nsFactoryEntry(aClass, aFactory));
 
-    MutexAutoLock lock(mLock);
+    SafeMutexAutoLock lock(mLock);
     nsFactoryEntry* oldf = mFactories.Get(aClass);
     if (oldf)
         return NS_ERROR_FACTORY_EXISTS;
@@ -1539,7 +1539,7 @@ nsComponentManagerImpl::UnregisterFactory(const nsCID& aClass,
     nsCOMPtr<nsISupports> dyingServiceObject;
 
     {
-        MutexAutoLock lock(mLock);
+        SafeMutexAutoLock lock(mLock);
         nsFactoryEntry* f = mFactories.Get(aClass);
         if (!f || f->mFactory != aFactory)
             return NS_ERROR_FACTORY_NOT_REGISTERED;
@@ -1666,7 +1666,7 @@ nsComponentManagerImpl::ContractIDToCID(const char *aContractID,
                                         nsCID * *_retval)
 {
     {
-        MutexAutoLock lock(mLock);
+        SafeMutexAutoLock lock(mLock);
         nsFactoryEntry* entry = mContractIDs.Get(nsDependentCString(aContractID));
         if (entry) {
             *_retval = (nsCID*) NS_Alloc(sizeof(nsCID));
@@ -1792,7 +1792,7 @@ nsFactoryEntry::GetFactory()
         if (!factory)
             return NULL;
 
-        MutexAutoLock lock(nsComponentManagerImpl::gComponentManager->mLock);
+        SafeMutexAutoLock lock(nsComponentManagerImpl::gComponentManager->mLock);
         // Threads can race to set mFactory
         if (!mFactory) {
             factory.swap(mFactory);

xpcom/components/nsComponentManager.h

@@ -64,6 +64,59 @@ extern const char staticComponentType[];
 
 extern const mozilla::Module kXPCOMModule;
 
+/**
+ * This is a wrapper around mozilla::Mutex which provides runtime
+ * checking for a deadlock where the same thread tries to lock a mutex while
+ * it is already locked. This checking is present in both debug and release
+ * builds.
+ */
+class SafeMutex
+{
+public:
+    SafeMutex(const char* name)
+        : mMutex(name)
+        , mOwnerThread(nullptr)
+    { }
+    ~SafeMutex()
+    { }
+
+    void Lock()
+    {
+        AssertNotCurrentThreadOwns();
+        mMutex.Lock();
+        MOZ_ASSERT(mOwnerThread == nullptr);
+        mOwnerThread = PR_GetCurrentThread();
+    }
+
+    void Unlock()
+    {
+        MOZ_ASSERT(mOwnerThread == PR_GetCurrentThread());
+        mOwnerThread = nullptr;
+        mMutex.Unlock();
+    }
+
+    void AssertCurrentThreadOwns() const
+    {
+        // This method is a debug-only check
+        MOZ_ASSERT(mOwnerThread == PR_GetCurrentThread());
+    }
+
+    MOZ_NEVER_INLINE void AssertNotCurrentThreadOwns() const
+    {
+        // This method is a release-mode check
+        if (PR_GetCurrentThread() == mOwnerThread) {
+            MOZ_CRASH();
+        }
+    }
+
+private:
+    mozilla::Mutex mMutex;
+    volatile PRThread* mOwnerThread;
+};
+
+typedef mozilla::BaseAutoLock<SafeMutex> SafeMutexAutoLock;
+typedef mozilla::BaseAutoUnlock<SafeMutex> SafeMutexAutoUnlock;
+
 class nsComponentManagerImpl MOZ_FINAL
     : public nsIComponentManager
     , public nsIServiceManager
@@ -112,7 +165,7 @@ public:
     nsDataHashtable<nsIDHashKey, nsFactoryEntry*> mFactories;
     nsDataHashtable<nsCStringHashKey, nsFactoryEntry*> mContractIDs;
 
-    mozilla::Mutex mLock;
+    SafeMutex mLock;
 
     static void InitializeStaticModules();
     static void InitializeModuleLocations();