pdns/unix_semaphore.cc

   1 /*
   2  * This file is part of PowerDNS or dnsdist.
   3  * Copyright -- PowerDNS.COM B.V. and its contributors
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of version 2 of the GNU General Public License as
   7  * published by the Free Software Foundation.
   8  *
   9  * In addition, for the avoidance of any doubt, permission is granted to
  10  * link this program with OpenSSL and to (re)distribute the binaries
  11  * produced as the result of such linking.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  21  */
  22 #ifdef HAVE_CONFIG_H
  23 #include "config.h"
  24 #endif
  25 #include "utility.hh"
  26 #include <cstring>
  27 #include <fcntl.h>
  28 #include <unistd.h>
  29 #include <stdlib.h>
  30 #include "pdnsexception.hh"
  31 #include "logger.hh"
  32 #include "misc.hh"
  33 #include <pwd.h>
  34 #include <grp.h>
  35 #include <sys/types.h>
  36
  37
  38 #if defined(_AIX) || defined(__APPLE__)
  39
  40 // Darwin 6.0 Compatible implementation, uses pthreads so it portable across more platforms.
  41
  42 #define SEM_VALUE_MAX 32767
  43 #define SEM_MAGIC     ((uint32_t) 0x09fa4012)
  44
  45 Semaphore::Semaphore(unsigned int value)
  46 {
  47   if (value > SEM_VALUE_MAX) {
  48     throw PDNSException("Cannot create semaphore: value too large");
  49   }
  50
  51   // Initialize
  52
  53   if (pthread_mutex_init(&m_lock, NULL) != 0) {
  54     throw PDNSException("Cannot create semaphore: cannot allocate mutex");
  55   }
  56
  57   if (pthread_cond_init(&m_gtzero, NULL) != 0) {
  58     pthread_mutex_destroy(&m_lock);
  59     throw PDNSException("Cannot create semaphore: cannot allocate condition");
  60   }
  61
  62   m_count = (uint32_t) value;
  63   m_nwaiters = 0;
  64   m_magic = SEM_MAGIC;
  65 }
  66
  67 int Semaphore::post()
  68 {
  69   pthread_mutex_lock(&m_lock);
  70
  71   m_count++;
  72   if (m_nwaiters > 0) {
  73     pthread_cond_signal(&m_gtzero);
  74   }
  75
  76   pthread_mutex_unlock(&m_lock);
  77
  78   return 0;
  79 }
  80
  81 int Semaphore::wait()
  82 {
  83   pthread_mutex_lock(&m_lock);
  84
  85   while (m_count == 0) {
  86     m_nwaiters++;
  87     pthread_cond_wait(&m_gtzero, &m_lock);
  88     m_nwaiters--;
  89   }
  90
  91   m_count--;
  92
  93   pthread_mutex_unlock(&m_lock);
  94
  95   return 0;
  96 }
  97
  98 int Semaphore::tryWait()
  99 {
 100   int retval = 0;
 101
 102   pthread_mutex_lock(&m_lock);
 103
 104   if (m_count > 0) {
 105     m_count--;
 106   } else {
 107     errno = EAGAIN;
 108     retval = -1;
 109   }
 110
 111   pthread_mutex_unlock(&m_lock);
 112
 113   return retval;
 114 }
 115
 116 int Semaphore::getValue(Semaphore::sem_value_t *sval)
 117 {
 118   pthread_mutex_lock(&m_lock);
 119   *sval = m_count;
 120   pthread_mutex_unlock(&m_lock);
 121
 122   return 0;
 123 }
 124
 125 Semaphore::~Semaphore()
 126 {
 127   // Make sure there are no waiters.
 128
 129   pthread_mutex_lock(&m_lock);
 130   if (m_nwaiters > 0) {
 131     pthread_mutex_unlock(&m_lock);
 132     //errno = EBUSY;
 133     //return -1;
 134   }
 135   pthread_mutex_unlock(&m_lock);
 136
 137   // Destroy it.
 138
 139   pthread_mutex_destroy(&m_lock);
 140   pthread_cond_destroy(&m_gtzero);
 141   m_magic = 0;
 142
 143   //return 0;
 144 }
 145
 146 #else /* not DARWIN from here on */
 147
 148
 149 Semaphore::Semaphore(unsigned int value)
 150 {
 151   m_pSemaphore=new sem_t;
 152   if (sem_init(m_pSemaphore, 0, value) == -1) {
 153     g_log << Logger::Error << "Cannot create semaphore: " << stringerror() << endl;
 154     exit(1);
 155   }
 156 }
 157
 158 int Semaphore::post()
 159 {
 160   return sem_post(m_pSemaphore);
 161 }
 162
 163 int Semaphore::wait()
 164 {
 165   int ret;
 166   do
 167     ret = sem_wait(m_pSemaphore);
 168   while (ret == -1 && errno == EINTR);
 169   return ret;
 170 }
 171 int Semaphore::tryWait()
 172 {
 173   return sem_trywait(m_pSemaphore);
 174 }
 175
 176 int Semaphore::getValue(Semaphore::sem_value_t *sval)
 177 {
 178   return sem_getvalue(m_pSemaphore, sval);
 179 }
 180
 181 Semaphore::~Semaphore()
 182 {
 183   delete m_pSemaphore;
 184 }
 185
 186 #endif