Bug 988464: log nsThreads still active at nsThreadManager::Shutdown() r=bsmedberg

build/automation.py.in

@@ -518,7 +518,7 @@ class Automation(object):
     env['NS_TRACE_MALLOC_DISABLE_STACKS'] = '1'
 
     # Set WebRTC logging in case it is not set yet
-    env.setdefault('NSPR_LOG_MODULES', 'signaling:5,mtransport:5,datachannel:5')
+    env.setdefault('NSPR_LOG_MODULES', 'signaling:5,mtransport:5,nsThreadManager:5')
     env.setdefault('R_LOG_LEVEL', '6')
     env.setdefault('R_LOG_DESTINATION', 'stderr')
     env.setdefault('R_LOG_VERBOSE', '1')

build/automationutils.py

@@ -498,7 +498,7 @@ def environment(xrePath, env=None, crashreporter=True, debugger=False, dmdPath=N
   env['MOZ_DISABLE_NONLOCAL_CONNECTIONS'] = '1'
 
   # Set WebRTC logging in case it is not set yet
-  env.setdefault('NSPR_LOG_MODULES', 'signaling:5,mtransport:5,datachannel:5')
+  env.setdefault('NSPR_LOG_MODULES', 'signaling:5,mtransport:5,datachannel:5,nsThreadManager:5')
   env.setdefault('R_LOG_LEVEL', '6')
   env.setdefault('R_LOG_DESTINATION', 'stderr')
   env.setdefault('R_LOG_VERBOSE', '1')

xpcom/threads/nsThread.h

@@ -74,6 +74,7 @@ protected:
   friend class nsNestedEventTarget;
 
   friend class nsThreadShutdownEvent;
+  friend class nsThreadManager;
 
   virtual ~nsThread();
 
@@ -156,11 +157,12 @@ protected:
     }
   };
 
-  // This lock protects access to mObserver, mEvents and mEventsAreDoomed.
-  // All of those fields are only modified on the thread itself (never from
-  // another thread).  This means that we can avoid holding the lock while
-  // using mObserver and mEvents on the thread itself.  When calling PutEvent
-  // on mEvents, we have to hold the lock to synchronize with PopEventQueue.
+  // This lock protects access to mObserver, mEvents and mEventsAreDoomed
+  // and mShutdownRequired.  All of those fields (except mShutdownRequired)
+  // are only modified on the thread itself (never from another thread).
+  // This means that we can avoid holding the lock while using mObserver
+  // and mEvents on the thread itself.  When calling PutEvent on mEvents,
+  // we have to hold the lock to synchronize with PopEventQueue.
   mozilla::Mutex mLock;
 
   nsCOMPtr<nsIThreadObserver> mObserver;

xpcom/threads/nsThreadManager.cpp

@@ -18,6 +18,21 @@
 
 using namespace mozilla;
 
+#ifdef PR_LOGGING
+static PRLogModuleInfo *
+GetThreadManagerLog()
+{
+  static PRLogModuleInfo *sLog;
+  if (!sLog)
+    sLog = PR_NewLogModule("nsThreadManager");
+  return sLog;
+}
+#endif
+#ifdef LOG
+#undef LOG
+#endif
+#define LOG(args) PR_LOG(GetThreadManagerLog(), PR_LOG_DEBUG, args)
+
 #ifdef XP_WIN
 #include <windows.h>
 DWORD gTLSThreadIDIndex = TlsAlloc();
@@ -163,12 +178,45 @@ nsThreadManager::Shutdown()
   // to shutdown.  This means that we have to preserve a mostly functioning
   // world until such time as the threads exit.
 
-  // Shutdown all threads that require it (join with threads that we created).
-  for (uint32_t i = 0; i < threads.Length(); ++i) {
-    nsThread* thread = threads[i];
-    if (thread->ShutdownRequired()) {
-      thread->Shutdown();
+  {
+#ifdef PR_LOGGING
+    // don't encourage other threads to run here by dumping log messages...
+    char buffer[4096];
+    char *ptr = buffer;
+    uint32_t leaked = 0;
+    for (uint32_t i = 0; i < threads.Length(); ++i) {
+      nsThread *thread = threads[i];
+      if (thread->ShutdownRequired()) {
+        leaked++;
+      }
     }
+    if (leaked > 0) {
+      PR_snprintf(ptr, sizeof(buffer), "*** %u threads active at %s\n", leaked, __FUNCTION__);
+      ptr += strlen(ptr);
+    }
+#endif
+
+    for (uint32_t i = 0; i < threads.Length(); ++i) {
+      nsThread *thread = threads[i];
+#ifdef PR_LOGGING
+      {
+        // So the PRThread can't go away while we're getting the name!
+        MutexAutoLock lock(thread->mLock);
+        if (thread->ShutdownRequired()) {
+          PRThread * prThread = thread->GetPRThread();
+          const char * name = PR_GetThreadName(prThread);
+          PR_snprintf(ptr, sizeof(buffer), "Thread %s (%p) still active\n", name ? name : "<unnamed>", thread);
+          ptr += strlen(ptr);
+        }
+      }
+#endif
+      if (thread->ShutdownRequired()) {
+        thread->Shutdown();
+      }
+    }
+#ifdef PR_LOGGING
+    LOG(("%s", buffer));
+#endif
   }
 
   // In case there are any more events somehow...