Backed out changeset ce0752c07ff6 (bug 1393046) under suspicion of causing asan failures in devtools tests a=backout CLOSED TREE

MozReview-Commit-ID: CKtxKuqiqVb

tools/profiler/core/platform.cpp

@@ -2639,46 +2639,6 @@ profiler_get_buffer_info_helper(uint32_t* aCurrentPosition,
   *aGeneration = ActivePS::Buffer(lock).mGeneration;
 }
 
-static void
-PollJSSamplingForCurrentThread()
-{
-  MOZ_RELEASE_ASSERT(CorePS::Exists());
-
-  PSAutoLock lock(gPSMutex);
-
-  ThreadInfo* info = TLSInfo::Info(lock);
-  if (!info) {
-    return;
-  }
-
-  info->PollJSSampling();
-}
-
-// When the profiler is started on a background thread, we can't synchronously
-// call PollJSSampling on the main thread's ThreadInfo. And the next regular
-// call to PollJSSampling on the main thread would only happen once the main
-// thread triggers a JS interrupt callback.
-// This means that all the JS execution between profiler_start() and the first
-// JS interrupt would happen with JS sampling disabled, and we wouldn't get any
-// JS function information for that period of time.
-// So in order to start JS sampling as soon as possible, we dispatch a runnable
-// to the main thread which manually calls PollJSSamplingForCurrentThread().
-// In some cases this runnable will lose the race with the next JS interrupt.
-// That's fine; PollJSSamplingForCurrentThread() is immune to redundant calls.
-static void
-TriggerPollJSSamplingOnMainThread()
-{
-  nsCOMPtr<nsIThread> mainThread;
-  nsresult rv = NS_GetMainThread(getter_AddRefs(mainThread));
-  if (NS_SUCCEEDED(rv) && mainThread) {
-    nsCOMPtr<nsIRunnable> task =
-      NS_NewRunnableFunction("TriggerPollJSSamplingOnMainThread", []() {
-        PollJSSamplingForCurrentThread();
-      });
-    SystemGroup::Dispatch(TaskCategory::Other, task.forget());
-  }
-}
-
 static void
 locked_profiler_start(PSLockRef aLock, int aEntries, double aInterval,
                       uint32_t aFeatures,
@@ -2729,11 +2689,6 @@ locked_profiler_start(PSLockRef aLock, int aEntries, double aInterval,
           // We can manually poll the current thread so it starts sampling
           // immediately.
           info->PollJSSampling();
-        } else if (info->IsMainThread()) {
-          // Dispatch a runnable to the main thread to call PollJSSampling(),
-          // so that we don't have wait for the next JS interrupt callback in
-          // order to start profiling JS.
-          TriggerPollJSSamplingOnMainThread();
         }
       }
     }
@@ -3121,7 +3076,17 @@ void
 profiler_js_interrupt_callback()
 {
   // This function runs on JS threads being sampled.
-  PollJSSamplingForCurrentThread();
+
+  MOZ_RELEASE_ASSERT(CorePS::Exists());
+
+  PSAutoLock lock(gPSMutex);
+
+  ThreadInfo* info = TLSInfo::Info(lock);
+  if (!info) {
+    return;
+  }
+
+  info->PollJSSampling();
 }
 
 double