95 lines
3.1 KiB
C
95 lines
3.1 KiB
C
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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// The Watchdog class creates a second thread that can Alarm if a specific
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// duration of time passes without proper attention. The duration of time is
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// specified at construction time. The Watchdog may be used many times by
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// simply calling Arm() (to start timing) and Disarm() (to reset the timer).
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// The Watchdog is typically used under a debugger, where the stack traces on
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// other threads can be examined if/when the Watchdog alarms.
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// Some watchdogs will be enabled or disabled via command line switches. To
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// facilitate such code, an "enabled" argument for the constuctor can be used
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// to permanently disable the watchdog. Disabled watchdogs don't even spawn
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// a second thread, and their methods call (Arm() and Disarm()) return very
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// quickly.
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#ifndef BASE_THREADING_WATCHDOG_H_
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#define BASE_THREADING_WATCHDOG_H_
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#include <string>
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#include "base/base_export.h"
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#include "base/compiler_specific.h"
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#include "base/synchronization/condition_variable.h"
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#include "base/synchronization/lock.h"
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#include "base/threading/platform_thread.h"
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#include "base/time/time.h"
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namespace base {
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class BASE_EXPORT Watchdog {
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public:
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// Constructor specifies how long the Watchdog will wait before alarming.
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Watchdog(const TimeDelta& duration,
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const std::string& thread_watched_name,
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bool enabled);
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virtual ~Watchdog();
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// Notify watchdog thread to finish up. Sets the state_ to SHUTDOWN.
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void Cleanup();
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// Returns true if we state_ is JOINABLE (which indicates that Watchdog has
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// exited).
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bool IsJoinable();
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// Start timing, and alarm when time expires (unless we're disarm()ed.)
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void Arm(); // Arm starting now.
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void ArmSomeTimeDeltaAgo(const TimeDelta& time_delta);
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void ArmAtStartTime(const TimeTicks start_time);
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// Reset time, and do not set off the alarm.
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void Disarm();
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// Alarm is called if the time expires after an Arm() without someone calling
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// Disarm(). This method can be overridden to create testable classes.
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virtual void Alarm();
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// Reset static data to initial state. Useful for tests, to ensure
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// they are independent.
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static void ResetStaticData();
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private:
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class ThreadDelegate : public PlatformThread::Delegate {
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public:
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explicit ThreadDelegate(Watchdog* watchdog) : watchdog_(watchdog) {
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}
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virtual void ThreadMain() OVERRIDE;
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private:
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void SetThreadName() const;
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Watchdog* watchdog_;
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};
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enum State {ARMED, DISARMED, SHUTDOWN, JOINABLE };
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bool enabled_;
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Lock lock_; // Mutex for state_.
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ConditionVariable condition_variable_;
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State state_;
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const TimeDelta duration_; // How long after start_time_ do we alarm?
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const std::string thread_watched_name_;
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PlatformThreadHandle handle_;
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ThreadDelegate delegate_; // Store it, because it must outlive the thread.
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TimeTicks start_time_; // Start of epoch, and alarm after duration_.
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DISALLOW_COPY_AND_ASSIGN(Watchdog);
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};
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} // namespace base
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#endif // BASE_THREADING_WATCHDOG_H_
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