mutex.cpp

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/*____________________________________________________________________________
        
        FreeAmp - The Free MP3 Player

        Portions Copyright (C) 1998-1999 EMusic.com

        This program is free software; you can redistribute it and/or modify
        it under the terms of the GNU General Public License as published by
        the Free Software Foundation; either version 2 of the License, or
        (at your option) any later version.

        This program is distributed in the hope that it will be useful,
        but WITHOUT ANY WARRANTY; without even the implied warranty of
        MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
        GNU General Public License for more details.

        You should have received a copy of the GNU General Public License
        along with this program; if not, write to the Free Software
        Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
        
        $Id: mutex.cpp,v 1.4 1999/10/19 07:12:48 elrod Exp $
____________________________________________________________________________*/
#include "config.h"

#include <string.h>
#include <pthread.h>
#include <iostream.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>

#include "mutex.h"

Mutex::Mutex(bool createOwned)
{

   pthread_mutexattr_t attr;

   m_iBusy = 0;
   m_tOwner = 0;
   pthread_cond_init(&m_tCond, NULL);

   pthread_mutexattr_init(&attr);

// If the mutexen become sane, we can do the following
// pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_PRIVATE);
// pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);

#ifdef SOLDEBUGMUTEX
   pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ERRORCHECK);
   // This is really, really, really helpful.
   // There's all sorts of multiple locking that shouldn't be going on,
   // and quite frankly, I don't know if freeamp will work at all with
   // "normal" non-debugging/recursive mutexen.
#endif

   if (!pthread_mutex_init(&m_mutex, &attr))
   {
     //	printf("created mutex %p\n", &m_mutex);
      if (createOwned)
      {
//	printf("with createOwned!\n");
         pthread_mutex_lock(&m_mutex);
      }
   }
   pthread_mutexattr_destroy(&attr);
}

Mutex::
~Mutex()
{

   pthread_mutex_destroy(&m_mutex);
   pthread_cond_destroy(&m_tCond);
}

/* This is the old Mutex::Acquire. Doesn't work with recursive acqs.
bool
Mutex::
Acquire(long timeout)
{
   bool      result = false;
   void *zot;

   zot = (void *) &m_mutex;
   //      printf("woii! Acquire %p!\n", zot);
 
   while (pthread_mutex_trylock(&m_mutex)) {
     //          printf("woii! %p sleeping!\n",&m_mutex);
     usleep(999999);
   }
   result = true;
   
   return (result);
} */

bool Mutex::Acquire(long timeout)
{
   pthread_mutex_lock(&m_mutex); 
   if (m_iBusy != 0)
   {
       if (m_tOwner != pthread_self())
       {     
	 //	 printf("m_tOwner %lx, pthread_self %lx\n", (long) m_tOwner, (long) pthread_self());
           do
           {
               if (timeout == WAIT_FOREVER)
               {
                   pthread_cond_wait(&m_tCond, &m_mutex);
               }     
               else
               {  
                   struct timespec sTime;
                   struct timeval  sNow;
   
                   gettimeofday(&sNow, NULL);
                   sTime.tv_sec = sNow.tv_sec;
                   sTime.tv_nsec = sNow.tv_usec + timeout;
                   if (sTime.tv_nsec >= 1000000)
                   {
                       sTime.tv_nsec -= 1000000;
                       sTime.tv_sec++;
                   }
                   sTime.tv_nsec *= 1000;

                   if (pthread_cond_timedwait(&m_tCond, &m_mutex, &sTime) ==
                      ETIMEDOUT)
                   {
                      pthread_mutex_unlock(&m_mutex);
                      return false;
                   }
               }

           } while(m_iBusy != 0);
       }
   }
   m_tOwner = pthread_self();
   m_iBusy++;
   pthread_mutex_unlock(&m_mutex);
           
   return true;
}


void Mutex::Release()
{
   int iOwnerShip;

//printf("Woi! Release %p!\n", (void *) &m_mutex);                   
   pthread_mutex_lock(&m_mutex);
   iOwnerShip = --m_iBusy;
   pthread_mutex_unlock(&m_mutex);

   if (iOwnerShip == 0)
       pthread_cond_signal(&m_tCond);

}

void Mutex::DumpMutex(void)
{
#if HAVE_LINUXTHREADS
   cerr << "pMutex = " << this << "\n";
   cerr << "Spinlock = " << m_mutex.m_spinlock << "\n";
   cerr << "Count = " << m_mutex.m_count << "\n";
   cerr << "Kind = " << m_mutex.m_owner << "\n";
   cerr << "Waiting = " << m_mutex.m_waiting.head << "\n";
#endif

}