Bug 1193838 - Make ProfileGatherer exist during the lifetime of a GeckoSampler. r=BenWa

--HG--
extra : commitid : GutYRbuADgV
extra : rebase_source : dc291977bb7ef43a024e26c83abb47b75a82b841

tools/profiler/core/GeckoSampler.cpp

@@ -247,6 +247,8 @@ GeckoSampler::GeckoSampler(double aInterval, int aEntrySize,
     mozilla::tasktracer::StartLogging();
   }
 #endif
+
+  mGatherer = new mozilla::ProfileGatherer(this);
 }
 
 GeckoSampler::~GeckoSampler()
@@ -279,6 +281,10 @@ GeckoSampler::~GeckoSampler()
 #if defined(XP_WIN)
   delete mIntelPowerGadget;
 #endif
+
+  // Cancel any in-flight async profile gatherering
+  // requests
+  mGatherer->Cancel();
 }
 
 void GeckoSampler::HandleSaveRequest()
@@ -416,17 +422,11 @@ UniquePtr<char[]> GeckoSampler::ToJSON(double aSinceTime)
 void GeckoSampler::ToJSObjectAsync(double aSinceTime,
                                   mozilla::dom::Promise* aPromise)
 {
-  if (NS_WARN_IF(mGatherer)) {
+  if (NS_WARN_IF(!mGatherer)) {
     return;
   }
 
-  mGatherer = new mozilla::ProfileGatherer(this, aSinceTime, aPromise);
-  mGatherer->Start();
-}
-
-void GeckoSampler::ProfileGathered()
-{
-  mGatherer = nullptr;
+  mGatherer->Start(aSinceTime, aPromise);
 }
 
 struct SubprocessClosure {

tools/profiler/core/GeckoSampler.h

@@ -127,8 +127,6 @@ class GeckoSampler: public Sampler {
 
   void GetBufferInfo(uint32_t *aCurrentPosition, uint32_t *aTotalSize, uint32_t *aGeneration);
 
-  void ProfileGathered();
-
 protected:
   // Called within a signal. This function must be reentrant
   virtual void InplaceTick(TickSample* sample);

tools/profiler/gecko/ProfileGatherer.cpp

@@ -14,13 +14,11 @@ namespace mozilla {
 
 NS_IMPL_ISUPPORTS0(ProfileGatherer)
 
-ProfileGatherer::ProfileGatherer(GeckoSampler* aTicker,
-                                 double aSinceTime,
-                                 Promise* aPromise)
-  : mPromise(aPromise)
-  , mTicker(aTicker)
-  , mSinceTime(aSinceTime)
+ProfileGatherer::ProfileGatherer(GeckoSampler* aTicker)
+  : mTicker(aTicker)
+  , mSinceTime(0)
   , mPendingProfiles(0)
+  , mGathering(false)
 {
 }
 
@@ -50,9 +48,23 @@ ProfileGatherer::WillGatherOOPProfile()
 }
 
 void
-ProfileGatherer::Start()
+ProfileGatherer::Start(double aSinceTime,
+                       Promise* aPromise)
 {
   MOZ_ASSERT(NS_IsMainThread());
+  if (mGathering) {
+    // If we're already gathering, reject the promise - this isn't going
+    // to end well.
+    if (aPromise) {
+      aPromise->MaybeReject(NS_ERROR_NOT_AVAILABLE);
+    }
+    return;
+  }
+
+  mSinceTime = aSinceTime;
+  mPromise = aPromise;
+  mGathering = true;
+  mPendingProfiles = 0;
 
   nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
   if (os) {
@@ -69,15 +81,19 @@ void
 ProfileGatherer::Finish()
 {
   MOZ_ASSERT(NS_IsMainThread());
+
+  if (!mTicker) {
+    // We somehow got called after we were cancelled! This shouldn't
+    // be possible, but doing a belt-and-suspenders check to be sure.
+    return;
+  }
+
   UniquePtr<char[]> buf = mTicker->ToJSON(mSinceTime);
 
   AutoJSAPI jsapi;
   if (NS_WARN_IF(!jsapi.Init(mPromise->GlobalJSObject()))) {
     // We're really hosed if we can't get a JS context for some reason.
-    // We'll tell the GeckoSampler that we've gathered the profile just
-    // so that it can drop the reference to this ProfileGatherer and maybe
-    // the user can try again.
-    mTicker->ProfileGathered();
+    Reset();
     return;
   }
 
@@ -104,7 +120,29 @@ ProfileGatherer::Finish()
     }
   }
 
-  mTicker->ProfileGathered();
+  Reset();
+}
+
+void
+ProfileGatherer::Reset()
+{
+  mSinceTime = 0;
+  mPromise = nullptr;
+  mPendingProfiles = 0;
+  mGathering = false;
+}
+
+void
+ProfileGatherer::Cancel()
+{
+  // The GeckoSampler is going away. If we have a Promise in flight, we
+  // should reject it.
+  if (mPromise) {
+    mPromise->MaybeReject(NS_ERROR_DOM_ABORT_ERR);
+  }
+
+  // Clear out the GeckoSampler reference, since it's being destroyed.
+  mTicker = nullptr;
 }
 
 } // namespace mozilla

tools/profiler/public/ProfileGatherer.h

@@ -16,21 +16,22 @@ class ProfileGatherer final : public nsISupports
 public:
   NS_DECL_ISUPPORTS
 
-  ProfileGatherer(GeckoSampler* aTicker,
-                  double aSinceTime,
-                  mozilla::dom::Promise* aPromise);
+  explicit ProfileGatherer(GeckoSampler* aTicker);
   void WillGatherOOPProfile();
   void GatheredOOPProfile();
-  void Start();
+  void Start(double aSinceTime, mozilla::dom::Promise* aPromise);
+  void Cancel();
 
 private:
   ~ProfileGatherer() {};
   void Finish();
+  void Reset();
 
   RefPtr<mozilla::dom::Promise> mPromise;
   GeckoSampler* mTicker;
   double mSinceTime;
   uint32_t mPendingProfiles;
+  bool mGathering;
 };
 
 } // namespace mozilla