Bug 1193838 - Allow ProfileGatherer to gather profiles from exiting processes. r=BenWa

--HG--
extra : commitid : IhyN838vNVU
extra : rebase_source : a91c87e3f9a087cd789bdb678651ab351357092a

dom/ipc/ContentChild.cpp

@@ -2965,6 +2965,15 @@ ContentChild::RecvShutdown()
 
     GetIPCChannel()->SetAbortOnError(false);
 
+#ifdef MOZ_ENABLE_PROFILER_SPS
+    if (profiler_is_active()) {
+        // We're shutting down while we were profiling. Send the
+        // profile up to the parent so that we don't lose this
+        // information.
+        Unused << RecvGatherProfile();
+    }
+#endif
+
     // Ignore errors here. If this fails, the parent will kill us after a
     // timeout.
     Unused << SendFinishShutdown();

dom/ipc/ContentParent.cpp

@@ -2094,6 +2094,12 @@ ContentParent::ActorDestroy(ActorDestroyReason why)
 
     mConsoleService = nullptr;
 
+#ifdef MOZ_ENABLE_PROFILER_SPS
+    if (mGatherer && !mProfile.IsEmpty()) {
+        mGatherer->OOPExitProfile(mProfile);
+    }
+#endif
+
     if (obs) {
         RefPtr<nsHashPropertyBag> props = new nsHashPropertyBag();
 

dom/plugins/ipc/PluginModuleParent.cpp

@@ -3185,8 +3185,7 @@ PluginProfilerObserver::Observe(nsISupports *aSubject,
     } else if (!strcmp(aTopic, "profiler-stopped")) {
         mPmp->StopProfiler();
     } else if (!strcmp(aTopic, "profiler-subprocess-gather")) {
-        RefPtr<ProfileGatherer> gatherer = static_cast<ProfileGatherer*>(aSubject);
-        mPmp->GatherAsyncProfile(gatherer);
+        mPmp->GatherAsyncProfile();
     } else if (!strcmp(aTopic, "profiler-subprocess")) {
         nsCOMPtr<nsIProfileSaveEvent> pse = do_QueryInterface(aSubject);
         mPmp->GatheredAsyncProfile(pse);

tools/profiler/gecko/ProfileGatherer.cpp

@@ -12,7 +12,16 @@ using mozilla::dom::Promise;
 
 namespace mozilla {
 
-NS_IMPL_ISUPPORTS0(ProfileGatherer)
+/**
+ * When a subprocess exits before we've gathered profiles, we'll
+ * store profiles for those processes until gathering starts. We'll
+ * only store up to MAX_SUBPROCESS_EXIT_PROFILES. The buffer is
+ * circular, so as soon as we receive another exit profile, we'll
+ * bump the oldest one out of the buffer.
+ */
+static const uint32_t MAX_SUBPROCESS_EXIT_PROFILES = 5;
+
+NS_IMPL_ISUPPORTS(ProfileGatherer, nsIObserver)
 
 ProfileGatherer::ProfileGatherer(GeckoSampler* aTicker)
   : mTicker(aTicker)
@@ -26,6 +35,13 @@ void
 ProfileGatherer::GatheredOOPProfile()
 {
   MOZ_ASSERT(NS_IsMainThread());
+  if (!mGathering) {
+    // If we're not actively gathering, then we don't actually
+    // care that we gathered a profile here. This can happen for
+    // processes that exit while profiling.
+    return;
+  }
+
   if (NS_WARN_IF(!mPromise)) {
     // If we're not holding on to a Promise, then someone is
     // calling us erroneously.
@@ -68,7 +84,9 @@ ProfileGatherer::Start(double aSinceTime,
 
   nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
   if (os) {
-    nsresult rv = os->NotifyObservers(this, "profiler-subprocess-gather", nullptr);
+    nsresult rv = os->AddObserver(this, "profiler-subprocess", false);
+    NS_WARN_IF(NS_FAILED(rv));
+    rv = os->NotifyObservers(this, "profiler-subprocess-gather", nullptr);
     NS_WARN_IF(NS_FAILED(rv));
   }
 
@@ -90,6 +108,12 @@ ProfileGatherer::Finish()
 
   UniquePtr<char[]> buf = mTicker->ToJSON(mSinceTime);
 
+  nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
+  if (os) {
+    nsresult rv = os->RemoveObserver(this, "profiler-subprocess");
+    NS_WARN_IF(NS_FAILED(rv));
+  }
+
   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.
@@ -145,4 +169,38 @@ ProfileGatherer::Cancel()
   mTicker = nullptr;
 }
 
+void
+ProfileGatherer::OOPExitProfile(const nsCString& aProfile)
+{
+  if (mExitProfiles.Length() >= MAX_SUBPROCESS_EXIT_PROFILES) {
+    mExitProfiles.RemoveElementAt(0);
+  }
+  mExitProfiles.AppendElement(aProfile);
+
+  // If a process exited while gathering, we need to make
+  // sure we decrement the counter.
+  if (mGathering) {
+    GatheredOOPProfile();
+  }
+}
+
+NS_IMETHODIMP
+ProfileGatherer::Observe(nsISupports* aSubject,
+                         const char* aTopic,
+                         const char16_t *someData)
+{
+  if (!strcmp(aTopic, "profiler-subprocess")) {
+    nsCOMPtr<nsIProfileSaveEvent> pse = do_QueryInterface(aSubject);
+    if (pse) {
+      for (size_t i = 0; i < mExitProfiles.Length(); ++i) {
+        if (!mExitProfiles[i].IsEmpty()) {
+          pse->AddSubProfile(mExitProfiles[i].get());
+        }
+      }
+      mExitProfiles.Clear();
+    }
+  }
+  return NS_OK;
+}
+
 } // namespace mozilla

tools/profiler/public/ProfileGatherer.h

@@ -11,22 +11,25 @@ class GeckoSampler;
 
 namespace mozilla {
 
-class ProfileGatherer final : public nsISupports
+class ProfileGatherer final : public nsIObserver
 {
 public:
   NS_DECL_ISUPPORTS
+  NS_DECL_NSIOBSERVER
 
   explicit ProfileGatherer(GeckoSampler* aTicker);
   void WillGatherOOPProfile();
   void GatheredOOPProfile();
   void Start(double aSinceTime, mozilla::dom::Promise* aPromise);
   void Cancel();
+  void OOPExitProfile(const nsCString& aProfile);
 
 private:
   ~ProfileGatherer() {};
   void Finish();
   void Reset();
 
+  nsTArray<nsCString> mExitProfiles;
   RefPtr<mozilla::dom::Promise> mPromise;
   GeckoSampler* mTicker;
   double mSinceTime;