Bug 965373 - When the profiler stops it doesn't stop the EventTracer thread; r=bgirard

---
 toolkit/xre/EventTracer.cpp   | 48 +++++++++++++++++++++++++++++++------------
 tools/profiler/nsProfiler.cpp |  3 +++
 2 files changed, 38 insertions(+), 13 deletions(-)

--HG--
extra : rebase_source : 249b164d232320bbec25de2b13d23ed87ffff842

toolkit/xre/EventTracer.cpp

@@ -58,6 +58,7 @@
 #include "mozilla/TimeStamp.h"
 #include "mozilla/WidgetTraceEvent.h"
 #include "nsDebug.h"
+#include "MainThreadUtils.h"
 #include <limits.h>
 #include <prenv.h>
 #include <prinrval.h>
@@ -75,13 +76,16 @@ using mozilla::TimeStamp;
 using mozilla::FireAndWaitForTracerEvent;
 
 namespace {
+  struct TracerStartClosure {
+    mozilla::Atomic<int> mLogTracing;
+  };
+}
 
-PRThread* sTracerThread = nullptr;
-bool sExit = false;
-
-struct TracerStartClosure {
-  bool mLogTracing;
-};
+static PRThread* sTracerThread = nullptr;
+static mozilla::Atomic<int> sExit(0);
+static int sStartCount = 0;
+static bool sLogging = false;
+static TracerStartClosure *sTracerStartClosure = nullptr;
 
 #ifdef MOZ_WIDGET_GONK
 class EventLoopLagDispatcher : public nsRunnable
@@ -118,7 +122,7 @@ class EventLoopLagDispatcher : public nsRunnable
  * settting the environment variable MOZ_INSTRUMENT_EVENT_LOOP_OUTPUT
  * to the name of a file to use.
  */
-void TracerThread(void *arg)
+static void TracerThread(void *arg)
 {
   PR_SetCurrentThreadName("Event Tracer");
 
@@ -209,29 +213,39 @@ void TracerThread(void *arg)
   delete threadArgs;
 }
 
-} // namespace
 
 namespace mozilla {
 
 bool InitEventTracing(bool aLog)
 {
-  if (sTracerThread)
+  MOZ_ASSERT(NS_IsMainThread());
+
+  // Keep track of how many times we were started and wait for everyone
+  // who needs us to tell us to shut down before we shut down
+  sStartCount++;
+
+  // If the tracer is already on we just make sure that the logging
+  // setting is on (if anyone asked for it)
+  if (sTracerThread) {
+    if (aLog)
+      sTracerStartClosure->mLogTracing = 1;
     return true;
+  }
 
   // Initialize the widget backend.
   if (!InitWidgetTracing())
     return false;
 
   // The tracer thread owns the object and will delete it.
-  TracerStartClosure* args = new TracerStartClosure();
-  args->mLogTracing = aLog;
+  sTracerStartClosure = new TracerStartClosure();
+  sTracerStartClosure->mLogTracing = aLog;
 
   // Create a thread that will fire events back at the
   // main thread to measure responsiveness.
   NS_ABORT_IF_FALSE(!sTracerThread, "Event tracing already initialized!");
   sTracerThread = PR_CreateThread(PR_USER_THREAD,
                                   TracerThread,
-                                  args,
+                                  sTracerStartClosure,
                                   PR_PRIORITY_NORMAL,
                                   PR_GLOBAL_THREAD,
                                   PR_JOINABLE_THREAD,
@@ -241,16 +255,24 @@ bool InitEventTracing(bool aLog)
 
 void ShutdownEventTracing()
 {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  // Wait for all starters to tell us they don't need us
+  sStartCount--;
+  if (sStartCount > 0)
+    return;
+
   if (!sTracerThread)
     return;
 
-  sExit = true;
+  sExit = 1;
   // Ensure that the tracer thread doesn't hang.
   SignalTracerThread();
 
   if (sTracerThread)
     PR_JoinThread(sTracerThread);
   sTracerThread = nullptr;
+  sTracerStartClosure = nullptr;
 
   // Allow the widget backend to clean up.
   CleanUpWidgetTracing();

tools/profiler/nsProfiler.cpp

@@ -92,6 +92,9 @@ NS_IMETHODIMP
 nsProfiler::StopProfiler()
 {
   profiler_stop();
+#ifdef MOZ_INSTRUMENT_EVENT_LOOP
+  mozilla::ShutdownEventTracing();
+#endif
   return NS_OK;
 }