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
  37   Lock(pthread_mutex_t *lock) : d_lock(lock)
  38   {
  39     if(g_singleThreaded)
  40       return;
  41     if((errno=pthread_mutex_lock(d_lock)))
  42       throw PDNSException("error acquiring lock: "+stringerror());
  43   }
  44   ~Lock()
  45   {
  46     if(g_singleThreaded)
  47       return;
  48
  49     pthread_mutex_unlock(d_lock);
  50   }
  51 };
  52
  53 class WriteLock
  54 {
  55   pthread_rwlock_t *d_lock;
  56 public:
  57
  58   WriteLock(pthread_rwlock_t *lock) : d_lock(lock)
  59   {
  60     if(g_singleThreaded)
  61       return;
  62
  63     if((errno=pthread_rwlock_wrlock(d_lock))) {
  64       throw PDNSException("error acquiring rwlock wrlock: "+stringerror());
  65     }
  66   }
  67   ~WriteLock()
  68   {
  69     if(g_singleThreaded)
  70       return;
  71
  72     pthread_rwlock_unlock(d_lock);
  73   }
  74 };
  75
  76 class TryWriteLock
  77 {
  78   pthread_rwlock_t *d_lock;
  79   bool d_havelock;
  80 public:
  81
  82   TryWriteLock(pthread_rwlock_t *lock) : d_lock(lock)
  83   {
  84     if(g_singleThreaded) {
  85       d_havelock=true;
  86       return;
  87     }
  88
  89     d_havelock=false;
  90     if((errno=pthread_rwlock_trywrlock(d_lock)) && errno!=EBUSY)
  91       throw PDNSException("error acquiring rwlock tryrwlock: "+stringerror());
  92     d_havelock=(errno==0);
  93   }
  94   ~TryWriteLock()
  95   {
  96     if(g_singleThreaded)
  97       return;
  98
  99     if(d_havelock)
 100       pthread_rwlock_unlock(d_lock);
 101   }
 102   bool gotIt()
 103   {
 104     if(g_singleThreaded)
 105       return true;
 106
 107     return d_havelock;
 108   }
 109 };
 110
 111 class TryReadLock
 112 {
 113   pthread_rwlock_t *d_lock;
 114   bool d_havelock;
 115 public:
 116
 117   TryReadLock(pthread_rwlock_t *lock) : d_lock(lock)
 118   {
 119     if(g_singleThreaded) {
 120       d_havelock=true;
 121       return;
 122     }
 123
 124     if((errno=pthread_rwlock_tryrdlock(d_lock)) && errno!=EBUSY)
 125       throw PDNSException("error acquiring rwlock tryrdlock: "+stringerror());
 126     d_havelock=(errno==0);
 127   }
 128   ~TryReadLock()
 129   {
 130     if(g_singleThreaded)
 131       return;
 132
 133     if(d_havelock)
 134       pthread_rwlock_unlock(d_lock);
 135   }
 136   bool gotIt()
 137   {
 138     if(g_singleThreaded)
 139       return true;
 140
 141     return d_havelock;
 142   }
 143 };
 144
 145
 146 class ReadLock
 147 {
 148   pthread_rwlock_t *d_lock;
 149 public:
 150
 151   ReadLock(pthread_rwlock_t *lock) : d_lock(lock)
 152   {
 153     if(g_singleThreaded)
 154       return;
 155
 156     if((errno=pthread_rwlock_rdlock(d_lock)))
 157       throw PDNSException("error acquiring rwlock tryrwlock: "+stringerror());
 158   }
 159   ~ReadLock()
 160   {
 161     if(g_singleThreaded)
 162       return;
 163
 164     pthread_rwlock_unlock(d_lock);
 165   }
 166
 167   void upgrade()
 168   {
 169     if(g_singleThreaded)
 170       return;
 171
 172     pthread_rwlock_unlock(d_lock);
 173     pthread_rwlock_wrlock(d_lock);
 174   }
 175 };
 176 #endif