pdns/lock.hh

   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 #ifndef LOCK_HH
  23 #define LOCK_HH
  24
  25 #include <pthread.h>
  26 #include <errno.h>
  27 #include "misc.hh"
  28 #include "pdnsexception.hh"
  29
  30 extern bool g_singleThreaded;
  31
  32 class Lock
  33 {
  34   pthread_mutex_t *d_lock;
  35 public:
  36   Lock(const Lock& rhs) = delete;
  37   Lock& operator=(const Lock& rhs) = delete;
  38
  39   Lock(pthread_mutex_t *lock) : d_lock(lock)
  40   {
  41     if(g_singleThreaded)
  42       return;
  43
  44     int err;
  45     if((err = pthread_mutex_lock(d_lock))) {
  46       errno = err;
  47       throw PDNSException("error acquiring lock: "+stringerror());
  48     }
  49   }
  50   ~Lock()
  51   {
  52     if(g_singleThreaded)
  53       return;
  54
  55     pthread_mutex_unlock(d_lock);
  56   }
  57 };
  58
  59 class WriteLock
  60 {
  61   pthread_rwlock_t *d_lock;
  62 public:
  63
  64   WriteLock(pthread_rwlock_t *lock) : d_lock(lock)
  65   {
  66     if(g_singleThreaded)
  67       return;
  68
  69     int err;
  70     if((err = pthread_rwlock_wrlock(d_lock))) {
  71       errno = err;
  72       throw PDNSException("error acquiring rwlock wrlock: "+stringerror());
  73     }
  74   }
  75   ~WriteLock()
  76   {
  77     if(g_singleThreaded)
  78       return;
  79     if(d_lock) // might have been moved
  80       pthread_rwlock_unlock(d_lock);
  81   }
  82
  83   WriteLock(WriteLock&& rhs)
  84   {
  85     d_lock = rhs.d_lock;
  86     rhs.d_lock=0;
  87   }
  88   WriteLock(const WriteLock& rhs) = delete;
  89   WriteLock& operator=(const WriteLock& rhs) = delete;
  90
  91
  92 };
  93
  94 class TryWriteLock
  95 {
  96   pthread_rwlock_t *d_lock;
  97   bool d_havelock;
  98 public:
  99   TryWriteLock(const TryWriteLock& rhs) = delete;
 100   TryWriteLock& operator=(const TryWriteLock& rhs) = delete;
 101
 102   TryWriteLock(pthread_rwlock_t *lock) : d_lock(lock)
 103   {
 104     if(g_singleThreaded) {
 105       d_havelock=true;
 106       return;
 107     }
 108
 109     d_havelock=false;
 110     int err;
 111     if((err = pthread_rwlock_trywrlock(d_lock)) && err!=EBUSY) {
 112       errno = err;
 113       throw PDNSException("error acquiring rwlock tryrwlock: "+stringerror());
 114     }
 115     d_havelock=(err==0);
 116   }
 117
 118   TryWriteLock(TryWriteLock&& rhs)
 119   {
 120     d_lock = rhs.d_lock;
 121     rhs.d_lock = nullptr;
 122     d_havelock = rhs.d_havelock;
 123     rhs.d_havelock = false;
 124   }
 125
 126
 127   ~TryWriteLock()
 128   {
 129     if(g_singleThreaded)
 130       return;
 131
 132     if(d_havelock && d_lock) // we might be moved
 133       pthread_rwlock_unlock(d_lock);
 134   }
 135   bool gotIt()
 136   {
 137     if(g_singleThreaded)
 138       return true;
 139
 140     return d_havelock;
 141   }
 142 };
 143
 144 class TryReadLock
 145 {
 146   pthread_rwlock_t *d_lock;
 147   bool d_havelock;
 148 public:
 149   TryReadLock(const TryReadLock& rhs) = delete;
 150   TryReadLock& operator=(const TryReadLock& rhs) = delete;
 151
 152   TryReadLock(pthread_rwlock_t *lock) : d_lock(lock)
 153   {
 154     if(g_singleThreaded) {
 155       d_havelock=true;
 156       return;
 157     }
 158
 159     int err;
 160     if((err = pthread_rwlock_tryrdlock(d_lock)) && err!=EBUSY) {
 161       errno = err;
 162       throw PDNSException("error acquiring rwlock tryrdlock: "+stringerror());
 163     }
 164     d_havelock=(err==0);
 165   }
 166   TryReadLock(TryReadLock&& rhs)
 167   {
 168     d_lock = rhs.d_lock;
 169     rhs.d_lock = nullptr;
 170     d_havelock = rhs.d_havelock;
 171     rhs.d_havelock = false;
 172   }
 173
 174   ~TryReadLock()
 175   {
 176     if(g_singleThreaded)
 177       return;
 178
 179     if(d_havelock && d_lock)
 180       pthread_rwlock_unlock(d_lock);
 181   }
 182   bool gotIt()
 183   {
 184     if(g_singleThreaded)
 185       return true;
 186
 187     return d_havelock;
 188   }
 189 };
 190
 191
 192 class ReadLock
 193 {
 194   pthread_rwlock_t *d_lock;
 195 public:
 196
 197   ReadLock(pthread_rwlock_t *lock) : d_lock(lock)
 198   {
 199     if(g_singleThreaded)
 200       return;
 201
 202     int err;
 203     if((err = pthread_rwlock_rdlock(d_lock))) {
 204       errno = err;
 205       throw PDNSException("error acquiring rwlock readlock: "+stringerror());
 206     }
 207   }
 208   ~ReadLock()
 209   {
 210     if(g_singleThreaded)
 211       return;
 212     if(d_lock) // may have been moved
 213       pthread_rwlock_unlock(d_lock);
 214   }
 215
 216   ReadLock(ReadLock&& rhs)
 217   {
 218     d_lock = rhs.d_lock;
 219     rhs.d_lock=0;
 220   }
 221   ReadLock(const ReadLock& rhs) = delete;
 222   ReadLock& operator=(const ReadLock& rhs) = delete;
 223 };
 224 #endif