include/Mutex.h

   1 /***************************************************************************
   2  *   Copyright (C) 2007 by www.databasecache.com                           *
   3  *   Contact: praba_tuty@databasecache.com                                 *
   4  *                                                                         *
   5  *   This program is free software; you can redistribute it and/or modify  *
   6  *   it under the terms of the GNU General Public License as published by  *
   7  *   the Free Software Foundation; either version 2 of the License, or     *
   8  *   (at your option) any later version.                                   *
   9  *                                                                         *
  10  *   This program is distributed in the hope that it will be useful,       *
  11  *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
  12  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
  13  *   GNU General Public License for more details.                          *
  14  *                                                                         *
  15   ***************************************************************************/
  16 #ifndef MUTEX_H
  17 #define MUTEX_H
  18 #include<os.h>
  19     #if defined(sparc)
  20     typedef unsigned char Lock;
  21     #elif defined (i686)  || defined(x86_64)
  22     typedef unsigned int Lock;
  23     #endif
  24 class Mutex
  25 {
  26
  27     #if defined(sparc) || defined(i686) || defined(x86_64)
  28     Lock lock;
  29     #else
  30     pthread_mutex_t mutex_;
  31     #endif
  32     public:
  33     char name[20];
  34     Mutex();
  35     int init();
  36     int init(char *name);
  37     int tryLock(int tries=0, int waitmsecs=0);
  38     int getLock(int procSlot, bool procAccount=true);
  39     int releaseLock(int procSlot, bool procAccount=true);
  40     int destroy();
  41     int recoverMutex();
  42     static int CAS(int *ptr, int oldVal, int newVal)
  43     {
  44         unsigned char ret;
  45         __asm__ __volatile__ (
  46                 "  lock\n"
  47                 "  cmpxchgl %2,%1\n"
  48                 "  sete %0\n"
  49                 : "=q" (ret), "=m" (*ptr)
  50                 : "r" (newVal), "m" (*ptr), "a" (oldVal)
  51                 : "memory");
  52
  53         //above assembly returns 0 in case of failure
  54         if (ret) return 0;
  55
  56         struct timeval timeout;
  57         timeout.tv_sec=0;
  58         timeout.tv_usec=1000;
  59         os::select(0,0,0,0, &timeout);
  60             __asm__ __volatile__ (
  61                 "  lock\n"
  62                 "  cmpxchgl %2,%1\n"
  63                 "  sete %0\n"
  64                 : "=q" (ret), "=m" (*ptr)
  65                 : "r" (newVal), "m" (*ptr), "a" (oldVal)
  66                 : "memory");
  67         //if (ret) return 0;  else {printf("DEBUG::CAS Fails %d-\n", ret); return 1; }
  68         if (ret) return 0;  else return 1;
  69
  70     }
  71     /*static int CASB(char *ptr, char oldVal, char newVal)
  72     {
  73         unsigned char ret;
  74         __asm__ __volatile__ ("lock; cmpxchgb %b1, %2"
  75                                : "=a" (ret)
  76                                : "m" (*(ptr), "q" (newVal), "0" (oldVal)
  77                                : "memory");
  78         printf("Value of ret is %d\n", ret);
  79         //above assembly returns 0 in case of failure
  80         if (ret) return 0;
  81         struct timeval timeout;
  82         timeout.tv_sec=0;
  83         timeout.tv_usec=500;
  84         os::select(0,0,0,0, &timeout);
  85         __asm__ __volatile__ ("lock; cmpxchgb %b1, %2"
  86                                : "=a" (ret)
  87                                : "m" (*(ptr), "q" (newVal), "0" (oldVal)
  88                                : "memory");
  89         if(!ret) { printf("DEBUG::CAS Fails\n"); return 1; } else return 0;
  90     }*/
  91 };
  92
  93 #endif