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| 1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 // The Watchdog class creates a second thread that can Alarm if a specific | |
| 6 // duration of time passes without proper attention. The duration of time is | |
| 7 // specified at construction time. The Watchdog may be used many times by | |
| 8 // simply calling Arm() (to start timing) and Disarm() (to reset the timer). | |
| 9 // The Watchdog is typically used under a debugger, where the stack traces on | |
| 10 // other threads can be examined if/when the Watchdog alarms. | |
| 11 | |
| 12 // Some watchdogs will be enabled or disabled via command line switches. To | |
| 13 // facilitate such code, an "enabled" argument for the constuctor can be used | |
| 14 // to permanently disable the watchdog. Disabled watchdogs don't even spawn | |
| 15 // a second thread, and their methods call (Arm() and Disarm()) return very | |
| 16 // quickly. | |
| 17 | |
| 18 #ifndef BASE_THREADING_WATCHDOG_H_ | |
| 19 #define BASE_THREADING_WATCHDOG_H_ | |
| 20 | |
| 21 #include <string> | |
| 22 | |
| 23 #include "base/base_export.h" | |
| 24 #include "base/compiler_specific.h" | |
| 25 #include "base/synchronization/condition_variable.h" | |
| 26 #include "base/synchronization/lock.h" | |
| 27 #include "base/threading/platform_thread.h" | |
| 28 #include "base/time/time.h" | |
| 29 | |
| 30 namespace base { | |
| 31 | |
| 32 class BASE_EXPORT Watchdog { | |
| 33 public: | |
| 34 // Constructor specifies how long the Watchdog will wait before alarming. | |
| 35 Watchdog(const TimeDelta& duration, | |
| 36 const std::string& thread_watched_name, | |
| 37 bool enabled); | |
| 38 virtual ~Watchdog(); | |
| 39 | |
| 40 // Notify watchdog thread to finish up. Sets the state_ to SHUTDOWN. | |
| 41 void Cleanup(); | |
| 42 | |
| 43 // Returns true if we state_ is JOINABLE (which indicates that Watchdog has | |
| 44 // exited). | |
| 45 bool IsJoinable(); | |
| 46 | |
| 47 // Start timing, and alarm when time expires (unless we're disarm()ed.) | |
| 48 void Arm(); // Arm starting now. | |
| 49 void ArmSomeTimeDeltaAgo(const TimeDelta& time_delta); | |
| 50 void ArmAtStartTime(const TimeTicks start_time); | |
| 51 | |
| 52 // Reset time, and do not set off the alarm. | |
| 53 void Disarm(); | |
| 54 | |
| 55 // Alarm is called if the time expires after an Arm() without someone calling | |
| 56 // Disarm(). This method can be overridden to create testable classes. | |
| 57 virtual void Alarm(); | |
| 58 | |
| 59 // Reset static data to initial state. Useful for tests, to ensure | |
| 60 // they are independent. | |
| 61 static void ResetStaticData(); | |
| 62 | |
| 63 private: | |
| 64 class ThreadDelegate : public PlatformThread::Delegate { | |
| 65 public: | |
| 66 explicit ThreadDelegate(Watchdog* watchdog) : watchdog_(watchdog) { | |
| 67 } | |
| 68 void ThreadMain() override; | |
| 69 | |
| 70 private: | |
| 71 void SetThreadName() const; | |
| 72 | |
| 73 Watchdog* watchdog_; | |
| 74 }; | |
| 75 | |
| 76 enum State {ARMED, DISARMED, SHUTDOWN, JOINABLE }; | |
| 77 | |
| 78 bool enabled_; | |
| 79 | |
| 80 Lock lock_; // Mutex for state_. | |
| 81 ConditionVariable condition_variable_; | |
| 82 State state_; | |
| 83 const TimeDelta duration_; // How long after start_time_ do we alarm? | |
| 84 const std::string thread_watched_name_; | |
| 85 PlatformThreadHandle handle_; | |
| 86 ThreadDelegate delegate_; // Store it, because it must outlive the thread. | |
| 87 | |
| 88 TimeTicks start_time_; // Start of epoch, and alarm after duration_. | |
| 89 | |
| 90 DISALLOW_COPY_AND_ASSIGN(Watchdog); | |
| 91 }; | |
| 92 | |
| 93 } // namespace base | |
| 94 | |
| 95 #endif // BASE_THREADING_WATCHDOG_H_ | |
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