Move some misc thread-related stuff from base to base/thread and into the bas...

base/threading/watchdog.h

+// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// The Watchdog class creates a second thread that can Alarm if a specific
+// duration of time passes without proper attention.  The duration of time is
+// specified at construction time.  The Watchdog may be used many times by
+// simply calling Arm() (to start timing) and Disarm() (to reset the timer).
+// The Watchdog is typically used under a debugger, where the stack traces on
+// other threads can be examined if/when the Watchdog alarms.
+
+// Some watchdogs will be enabled or disabled via command line switches. To
+// facilitate such code, an "enabled" argument for the constuctor can be used
+// to permanently disable the watchdog.  Disabled watchdogs don't even spawn
+// a second thread, and their methods call (Arm() and Disarm()) return very
+// quickly.
+
+#ifndef BASE_THREADING_WATCHDOG_H_
+#define BASE_THREADING_WATCHDOG_H_
+#pragma once
+
+#include <string>
+
+#include "base/condition_variable.h"
+#include "base/lock.h"
+#include "base/platform_thread.h"
+#include "base/time.h"
+
+namespace base {
+
+class Watchdog {
+ public:
+  // Constructor specifies how long the Watchdog will wait before alarming.
+  Watchdog(const base::TimeDelta& duration,
+           const std::string& thread_watched_name,
+           bool enabled);
+  virtual ~Watchdog();
+
+  // Start timing, and alarm when time expires (unless we're disarm()ed.)
+  void Arm();  // Arm  starting now.
+  void ArmSomeTimeDeltaAgo(const base::TimeDelta& time_delta);
+  void ArmAtStartTime(const base::TimeTicks start_time);
+
+  // Reset time, and do not set off the alarm.
+  void Disarm();
+
+  // Alarm is called if the time expires after an Arm() without someone calling
+  // Disarm().  This method can be overridden to create testable classes.
+  virtual void Alarm();
+
+  // Reset static data to initial state. Useful for tests, to ensure
+  // they are independent.
+  static void ResetStaticData();
+
+ private:
+  class ThreadDelegate : public PlatformThread::Delegate {
+   public:
+    explicit ThreadDelegate(Watchdog* watchdog) : watchdog_(watchdog) {
+    }
+    virtual void ThreadMain();
+   private:
+    Watchdog* watchdog_;
+
+    void SetThreadName() const;
+  };
+
+  enum State {ARMED, DISARMED, SHUTDOWN };
+
+  bool init_successful_;
+
+  Lock lock_;  // Mutex for state_.
+  ConditionVariable condition_variable_;
+  State state_;
+  const base::TimeDelta duration_;  // How long after start_time_ do we alarm?
+  const std::string thread_watched_name_;
+  PlatformThreadHandle handle_;
+  ThreadDelegate delegate_;  // Store it, because it must outlive the thread.
+
+  base::TimeTicks start_time_;  // Start of epoch, and alarm after duration_.
+
+  // When the debugger breaks (when we alarm), all the other alarms that are
+  // armed will expire (also alarm).  To diminish this effect, we track any
+  // delay due to debugger breaks, and we *try* to adjust the effective start
+  // time of other alarms to step past the debugging break.
+  // Without this safety net, any alarm will typically trigger a host of follow
+  // on alarms from callers that specify old times.
+  static Lock static_lock_;  // Lock for access of static data...
+  // When did we last alarm and get stuck (for a while) in a debugger?
+  static base::TimeTicks last_debugged_alarm_time_;
+  // How long did we sit on a break in the debugger?
+  static base::TimeDelta last_debugged_alarm_delay_;
+
+  DISALLOW_COPY_AND_ASSIGN(Watchdog);
+};
+
+}  // namespace base
+
+#endif  // BASE_THREADING_WATCHDOG_H_