ceph/src/common/Timer.h

   1 // -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
   2 // vim: ts=8 sw=2 smarttab
   3 /*
   4  * Ceph - scalable distributed file system
   5  *
   6  * Copyright (C) 2004-2006 Sage Weil <sage@newdream.net>
   7  *
   8  * This is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License version 2.1, as published by the Free Software
  11  * Foundation.  See file COPYING.
  12  *
  13  */
  14
  15 #ifndef CEPH_TIMER_H
  16 #define CEPH_TIMER_H
  17
  18 #include "Cond.h"
  19 #include "Mutex.h"
  20
  21 class CephContext;
  22 class Context;
  23 class SafeTimerThread;
  24
  25 class SafeTimer
  26 {
  27   CephContext *cct;
  28   Mutex& lock;
  29   Cond cond;
  30   bool safe_callbacks;
  31
  32   friend class SafeTimerThread;
  33   SafeTimerThread *thread;
  34
  35   void timer_thread();
  36   void _shutdown();
  37
  38   std::multimap<utime_t, Context*> schedule;
  39   std::map<Context*, std::multimap<utime_t, Context*>::iterator> events;
  40   bool stopping;
  41
  42   void dump(const char *caller = 0) const;
  43
  44 public:
  45   // This class isn't supposed to be copied
  46   SafeTimer(const SafeTimer&) = delete;
  47   SafeTimer& operator=(const SafeTimer&) = delete;
  48
  49   /* Safe callbacks determines whether callbacks are called with the lock
  50    * held.
  51    *
  52    * safe_callbacks = true (default option) guarantees that a cancelled
  53    * event's callback will never be called.
  54    *
  55    * Under some circumstances, holding the lock can cause lock cycles.
  56    * If you are able to relax requirements on cancelled callbacks, then
  57    * setting safe_callbacks = false eliminates the lock cycle issue.
  58    * */
  59   SafeTimer(CephContext *cct, Mutex &l, bool safe_callbacks=true);
  60   ~SafeTimer();
  61
  62   /* Call with the event_lock UNLOCKED.
  63    *
  64    * Cancel all events and stop the timer thread.
  65    *
  66    * If there are any events that still have to run, they will need to take
  67    * the event_lock first. */
  68   void init();
  69   void shutdown();
  70
  71   /* Schedule an event in the future
  72    * Call with the event_lock LOCKED */
  73   void add_event_after(double seconds, Context *callback);
  74   void add_event_at(utime_t when, Context *callback);
  75
  76   /* Cancel an event.
  77    * Call with the event_lock LOCKED
  78    *
  79    * Returns true if the callback was cancelled.
  80    * Returns false if you never addded the callback in the first place.
  81    */
  82   bool cancel_event(Context *callback);
  83
  84   /* Cancel all events.
  85    * Call with the event_lock LOCKED
  86    *
  87    * When this function returns, all events have been cancelled, and there are no
  88    * more in progress.
  89    */
  90   void cancel_all_events();
  91
  92 };
  93
  94 #endif