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#include <iostream>
#include <stdlib.h>
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "debug.h"
#include "thread.h"
#include "multex.h"
using namespace std;
// pthreads-based implementation
Multex::Multex(int limit) : PTMutex(), lockcount(0), limit(limit)
{
static int ser=0;
serialno=++ser; // Giving each multex a serial number makes debugging easier.
for(int i=0;i<MULTEX_THREADS_MAX;++i)
{
counttable[i].id=0;
counttable[i].count=0;
}
pthread_cond_init(&cond,0);
}
Multex::~Multex()
{
}
// ObtainMultex - obtains the multex if the thread limit has not yet been reached,
// waits if this thread doesn't already have a lock and no further threads are allowed.
void Multex::ObtainMultex()
{
// Debug[TRACE] << "Multex " << serialno << ": Obtaining from " << long(Thread::GetThreadID()) << endl;
PTMutex::ObtainMutex();
while(lockcount>=limit)
{
pthread_cond_wait(&cond,&mutex);
}
Increment();
// Dump();
PTMutex::ReleaseMutex();
}
bool Multex::AttemptMultex()
{
// Debug[TRACE] << "Multex " << serialno << ": AttemptMutex from " << long(Thread::GetThreadID()) << endl;
bool result=false;
PTMutex::ObtainMutex();
if(lockcount<limit)
{
// Debug[TRACE] << "Obtained multex lock - lock count: " << lockcount << endl;
Increment();
// Dump();
result=true;
}
PTMutex::ReleaseMutex();
return(result);
}
void Multex::ReleaseMultex()
{
// Debug[TRACE] << "Multex " << serialno << ": ReleaseMutex from " << long(Thread::GetThreadID()) << endl;
PTMutex::ObtainMutex();
Decrement();
// Dump();
pthread_cond_broadcast(&cond);
PTMutex::ReleaseMutex();
}
void Multex::SetThreadLimit(int l)
{
limit=l;
}
void Multex::Increment()
{
++lockcount;
// Find the current thread in the table and increment its count
#ifdef WIN32
void *current=pthread_self().p;
#else
pthread_t current=pthread_self();
#endif
// Debug[TRACE] << "Increment - searching for thread: " << current << endl;
for(int i=0;i<MULTEX_THREADS_MAX;++i)
{
if(counttable[i].id==current)
{
// Debug[TRACE] << "found" << endl;
++counttable[i].count;
return;
}
}
// If none found, add a new entry, and set the count to 1;
// Debug[TRACE] << "Increment - searching for free slot" << endl;
while(1)
{
for(int i=0;i<MULTEX_THREADS_MAX;++i)
{
if(counttable[i].id==0)
{
// Debug[TRACE] << "found" << endl;
counttable[i].id=current;
counttable[i].count=1;
return;
}
}
// If there were no free slots, complain.
Debug[WARN] << "Multex: thread table full - waiting..." << endl;
pthread_cond_wait(&cond,&mutex);
Debug[WARN] << "Multex - trying again to find a free slot... " << endl;
}
}
void Multex::Decrement(bool shared)
{
--lockcount;
#ifdef WIN32
void *current=pthread_self().p;
#else
pthread_t current=pthread_self();
#endif
// Debug[TRACE] << "Decrement - searching for thread: " << current << endl;
for(int i=0;i<MULTEX_THREADS_MAX;++i)
{
if(counttable[i].id==current)
{
--counttable[i].count;
if(counttable[i].count==0)
counttable[i].id=0;
return;
}
}
// If thread was not found, complain.
// Debug[TRACE] << "Multex: thread not found in table." << endl;
}
void Multex::Dump()
{
Debug[TRACE] << "Locks held: " << lockcount << endl;
for(int i=0;i<MULTEX_THREADS_MAX;++i)
{
if(counttable[i].id)
Debug[TRACE] << "Thread: " << counttable[i].id << ", count: " << counttable[i].count << endl;
}
}
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