1 /*- 2 * Copyright (c) 2011, 2012, 2013 Spectra Logic Corporation 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions, and the following disclaimer, 10 * without modification. 11 * 2. Redistributions in binary form must reproduce at minimum a disclaimer 12 * substantially similar to the "NO WARRANTY" disclaimer below 13 * ("Disclaimer") and any redistribution must be conditioned upon 14 * including a substantially similar Disclaimer requirement for further 15 * binary redistribution. 16 * 17 * NO WARRANTY 18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR 21 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 22 * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 26 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING 27 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28 * POSSIBILITY OF SUCH DAMAGES. 29 * 30 * Authors: Justin T. Gibbs (Spectra Logic Corporation) 31 */ 32 33 /** 34 * \file callout.h 35 * 36 * \brief Interface for timer based callback services. 37 * 38 * Header requirements: 39 * 40 * #include <sys/time.h> 41 * 42 * #include <list> 43 */ 44 45 #ifndef _CALLOUT_H_ 46 #define _CALLOUT_H_ 47 48 /** 49 * \brief Type of the function callback from a Callout. 50 */ 51 typedef void CalloutFunc_t(void *); 52 53 /** 54 * \brief Interface to a schedulable one-shot timer with the granularity 55 * of the system clock (see setitimer(2)). 56 * 57 * Determination of callback expiration is triggered by the SIGALRM 58 * signal. Callout callbacks are always delivered from Zfsd's event 59 * processing loop. 60 * 61 * Periodic actions can be triggered via the Callout mechanisms by 62 * resetting the Callout from within its callback. 63 */ 64 class Callout 65 { 66 public: 67 68 /** 69 * Initialize the Callout subsystem. 70 */ 71 static void Init(); 72 73 /** 74 * Function called (via SIGALRM) when our interval 75 * timer expires. 76 */ 77 static void AlarmSignalHandler(int); 78 79 /** 80 * Execute callbacks for all callouts that have the same 81 * expiration time as the first callout in the list. 82 */ 83 static void ExpireCallouts(); 84 85 /** Constructor. */ 86 Callout(); 87 88 /** 89 * Returns true if callout has not been stopped, 90 * or deactivated since the last time the callout was 91 * reset. 92 */ 93 bool IsActive() const; 94 95 /** 96 * Returns true if callout is still waiting to expire. 97 */ 98 bool IsPending() const; 99 100 /** 101 * Disestablish a callout. 102 */ 103 bool Stop(); 104 105 /** 106 * \brief Establish or change a timeout. 107 * 108 * \param interval Timeval indicating the time which must elapse 109 * before this callout fires. 110 * \param func Pointer to the callback function 111 * \param arg Argument pointer to pass to callback function 112 * 113 * \return Cancellation status. 114 * true: The previous callback was pending and therefore 115 * was cancelled. 116 * false: The callout was not pending at the time of this 117 * reset request. 118 * In all cases, a new callout is established. 119 */ 120 bool Reset(const timeval &interval, CalloutFunc_t *func, void *arg); 121 122 /** 123 * \brief Calculate the remaining time until this Callout's timer 124 * expires. 125 * 126 * The return value will be slightly greater than the actual time to 127 * expiry. 128 * 129 * If the callout is not pending, returns INT_MAX. 130 */ 131 timeval TimeRemaining() const; 132 133 private: 134 /** 135 * All active callouts sorted by expiration time. The callout 136 * with the nearest expiration time is at the head of the list. 137 */ 138 static std::list<Callout *> s_activeCallouts; 139 140 /** 141 * The interval timer has expired. This variable is set from 142 * signal handler context and tested from Zfsd::EventLoop() 143 * context via ExpireCallouts(). 144 */ 145 static bool s_alarmFired; 146 147 /** 148 * Time, relative to others in the active list, until 149 * this callout is fired. 150 */ 151 timeval m_interval; 152 153 /** Callback function argument. */ 154 void *m_arg; 155 156 /** 157 * The callback function associated with this timer 158 * entry. 159 */ 160 CalloutFunc_t *m_func; 161 162 /** State of this callout. */ 163 bool m_pending; 164 }; 165 166 //- Callout public const methods ---------------------------------------------- 167 inline bool 168 Callout::IsPending() const 169 { 170 return (m_pending); 171 } 172 173 //- Callout public methods ---------------------------------------------------- 174 inline 175 Callout::Callout() 176 : m_arg(0), 177 m_func(NULL), 178 m_pending(false) 179 { 180 timerclear(&m_interval); 181 } 182 183 #endif /* CALLOUT_H_ */ 184