diff -r 000000000000 -r 6474c204b198 xpcom/threads/ThreadStackHelper.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xpcom/threads/ThreadStackHelper.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,102 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ThreadStackHelper_h
+#define mozilla_ThreadStackHelper_h
+
+#include "mozilla/ThreadHangStats.h"
+
+#include "GeckoProfiler.h"
+
+#include <stddef.h>
+
+#if defined(XP_LINUX)
+#include <signal.h>
+#include <semaphore.h>
+#include <sys/types.h>
+#elif defined(XP_WIN)
+#include <windows.h>
+#elif defined(XP_MACOSX)
+#include <mach/mach.h>
+#endif
+
+namespace mozilla {
+
+/**
+ * ThreadStackHelper is used to retrieve the profiler pseudo-stack of a
+ * thread, as an alternative of using the profiler to take a profile.
+ * The target thread first declares an ThreadStackHelper instance;
+ * then another thread can call ThreadStackHelper::GetStack to retrieve
+ * the pseudo-stack of the target thread at that instant.
+ *
+ * Only non-copying labels are included in the stack, which means labels
+ * with custom text and markers are not included.
+ */
+class ThreadStackHelper
+{
+public:
+  typedef Telemetry::HangHistogram::Stack Stack;
+
+private:
+#ifdef MOZ_ENABLE_PROFILER_SPS
+  const PseudoStack* const mPseudoStack;
+#endif
+  Stack mStackBuffer;
+  size_t mMaxStackSize;
+
+  bool PrepareStackBuffer(Stack& aStack);
+  void FillStackBuffer();
+
+public:
+  /**
+   * Initialize ThreadStackHelper. Must be called from main thread.
+   */
+  static void Startup();
+  /**
+   * Uninitialize ThreadStackHelper. Must be called from main thread.
+   */
+  static void Shutdown();
+
+  /**
+   * Create a ThreadStackHelper instance targeting the current thread.
+   */
+  ThreadStackHelper();
+
+  ~ThreadStackHelper();
+
+  /**
+   * Retrieve the current pseudostack of the thread associated
+   * with this ThreadStackHelper.
+   *
+   * @param aStack Stack instance to be filled.
+   */
+  void GetStack(Stack& aStack);
+
+#if defined(XP_LINUX)
+private:
+  static int sInitialized;
+  static sem_t sSem;
+  static struct sigaction sOldSigAction;
+  static ThreadStackHelper* sCurrent;
+
+  static void SigAction(int aSignal, siginfo_t* aInfo, void* aContext);
+
+  pid_t mThreadID;
+
+#elif defined(XP_WIN)
+private:
+  bool mInitialized;
+  HANDLE mThreadID;
+
+#elif defined(XP_MACOSX)
+private:
+  thread_act_t mThreadID;
+
+#endif
+};
+
+} // namespace mozilla
+
+#endif // mozilla_ThreadStackHelper_h