dep/src/zthread/posix/Monitor.cxx

   1 /*
   2  * Copyright (c) 2005, Eric Crahen
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a copy
   5  * of this software and associated documentation files (the "Software"), to deal
   6  * in the Software without restriction, including without limitation the rights
   7  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   8  * copies of the Software, and to permit persons to whom the Software is furnished
   9  * to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice shall be included in all
  12  * copies or substantial portions of the Software.
  13  *
  14  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  15  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  17  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
  18  * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  19  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  20  *
  21  */
  22
  23 #include "Monitor.h"
  24 #include "../Debug.h"
  25 #include "../TimeStrategy.h"
  26
  27 #include <errno.h>
  28 #include <assert.h>
  29 #include <signal.h>
  30
  31 namespace ZThread {
  32
  33 Monitor::Monitor() : _owner(0), _waiting(false) {
  34
  35   pthread_cond_init(&_waitCond, 0);
  36   pthread_mutex_init(&_waitLock, 0);
  37
  38 }
  39
  40 Monitor::~Monitor() {
  41
  42   assert(!_waiting);
  43
  44   pthread_cond_destroy(&_waitCond);
  45   pthread_mutex_destroy(&_waitLock);
  46
  47 }
  48
  49 Monitor::STATE Monitor::wait(unsigned long ms) {
  50
  51   // Update the owner on first use. The owner will not change, each
  52   // thread waits only on a single Monitor and a Monitor is never
  53   // shared
  54   if(_owner == 0)
  55     _owner = pthread_self();
  56
  57   STATE state(INVALID);
  58
  59   // Serialize access to the state of the Monitor
  60   // and test the state to determine if a wait is needed.
  61
  62   pthread_mutex_lock(&_waitLock);
  63
  64   if(pending(ANYTHING)) {
  65
  66     // Return without waiting when possible
  67     state = next();
  68
  69     pthread_mutex_unlock(&_waitLock);
  70     return state;
  71
  72   }
  73
  74   // Unlock the external lock if a wait() is probably needed.
  75   // Access to the state is still serial.
  76   _lock.release();
  77
  78   // Wait for a transition in the state that is of interest, this
  79   // allows waits to exclude certain flags (e.g. INTERRUPTED)
  80   // for a single wait() w/o actually discarding those flags -
  81   // they will remain set until a wait interested in those flags
  82   // occurs.
  83   //  if(!currentState(interest)) {
  84
  85   // Wait, ignoring signals
  86   _waiting = true;
  87   int status = 0;
  88
  89   if(ms == 0) { // Wait forever
  90
  91     do { // ignore signals unless the state is interesting
  92       status = pthread_cond_wait(&_waitCond, &_waitLock);
  93     } while(status == EINTR && !pending(ANYTHING));
  94
  95     // Akwaken only when a state is pending
  96     assert(status == 0);
  97
  98   } else {
  99
 100     // Find the target time
 101     TimeStrategy t;
 102
 103     ms += t.milliseconds();
 104
 105     unsigned long s = t.seconds() + (ms / 1000);
 106     ms %= 1000;
 107
 108     // Convert to a timespec
 109     struct ::timespec timeout;
 110
 111     timeout.tv_sec = s;
 112     timeout.tv_nsec = ms*1000000;
 113
 114     // Wait ignoring signals until the state is interesting
 115     do {
 116
 117       // When a timeout occurs, update the state to reflect that.
 118       status = pthread_cond_timedwait(&_waitCond, &_waitLock, &timeout);
 119
 120     } while(status == EINTR && !pending(ANYTHING));
 121
 122     // Akwaken only when a state is pending or when the timeout expired
 123     assert(status == 0 || status == ETIMEDOUT);
 124
 125     if(status == ETIMEDOUT)
 126       push(TIMEDOUT);
 127
 128   }
 129
 130   // Get the next available STATE
 131   state = next();
 132   _waiting = false;
 133
 134   pthread_mutex_unlock(&_waitLock);
 135
 136   // Reaquire the external lock, keep from deadlocking threads calling
 137   // notify(), interrupt(), etc.
 138
 139   _lock.acquire();
 140
 141   return state;
 142
 143 }
 144
 145
 146 bool Monitor::interrupt() {
 147
 148   // Serialize access to the state
 149   pthread_mutex_lock(&_waitLock);
 150
 151   bool wasInterruptable = !pending(INTERRUPTED);
 152   bool hadWaiter = _waiting;
 153
 154   if(wasInterruptable) {
 155
 156     // Update the state & wake the waiter if there is one
 157     push(INTERRUPTED);
 158
 159     wasInterruptable = false;
 160
 161     if(hadWaiter && !masked(Monitor::INTERRUPTED))
 162       pthread_cond_signal(&_waitCond);
 163     else
 164       wasInterruptable = !pthread_equal(_owner, pthread_self());
 165
 166   }
 167
 168   pthread_mutex_unlock(&_waitLock);
 169
 170   // Only returns true when an interrupted thread is not currently blocked
 171   return wasInterruptable;
 172
 173 }
 174
 175 bool Monitor::isInterrupted() {
 176
 177   // Serialize access to the state
 178   pthread_mutex_lock(&_waitLock);
 179
 180   bool wasInterrupted = pending(INTERRUPTED);
 181
 182   clear(INTERRUPTED);
 183
 184   pthread_mutex_unlock(&_waitLock);
 185
 186   return wasInterrupted;
 187
 188 }
 189
 190 bool Monitor::isCanceled() {
 191
 192   // Serialize access to the state
 193   pthread_mutex_lock(&_waitLock);
 194
 195   bool wasCanceled = examine(CANCELED);
 196
 197   if(pthread_equal(_owner, pthread_self()))
 198     clear(INTERRUPTED);
 199
 200   pthread_mutex_unlock(&_waitLock);
 201
 202   return wasCanceled;
 203
 204 }
 205
 206 bool Monitor::cancel() {
 207
 208   // Serialize access to the state
 209   pthread_mutex_lock(&_waitLock);
 210
 211   bool wasInterrupted = !pending(INTERRUPTED);
 212   bool hadWaiter = _waiting;
 213
 214   push(CANCELED);
 215
 216   if(wasInterrupted) {
 217
 218     // Update the state & wake the waiter if there is one
 219     push(INTERRUPTED);
 220
 221     if(hadWaiter && !masked(Monitor::INTERRUPTED))
 222       pthread_cond_signal(&_waitCond);
 223
 224   }
 225
 226   pthread_mutex_unlock(&_waitLock);
 227
 228   return wasInterrupted;
 229
 230 }
 231
 232 bool Monitor::notify() {
 233
 234   // Serialize access to the state
 235   pthread_mutex_lock(&_waitLock);
 236
 237   bool wasNotifyable = !pending(INTERRUPTED);
 238
 239   if(wasNotifyable) {
 240
 241     // Set the flag and wake the waiter if there
 242     // is one
 243     push(SIGNALED);
 244
 245     if(_waiting)
 246       pthread_cond_signal(&_waitCond);
 247
 248   }
 249
 250   pthread_mutex_unlock(&_waitLock);
 251
 252   return wasNotifyable;
 253
 254 }
 255
 256 } // namespace ZThread
 257