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Re: Handle leak when using pthread mutex with win32 api threads
- From: Dmitrii Sernii <bogolt at gmail dot com>
- To: pthreads-win32 at sources dot redhat dot com
- Date: Sat, 5 Mar 2005 15:31:24 +0200
- Subject: Re: Handle leak when using pthread mutex with win32 api threads
- Reply-to: Dmitrii Sernii <bogolt at gmail dot com>
> > > static pthread_mutex_t mutex(PTHREAD_RECURSIVE_MUTEX_INITIALIZER);
> >
> > that line above is not thread safe. you might initialize the same
> > mutex multiple times. Not good.
> >
>
> The handle leak comes about because, in pthreads-win32, pthread_mutex_t
> is only a pointer, and the actual mutex struct is malloced by the
> library, in this case, the first time you call pthread_mutex_lock().
> That is, the library just calls pthread_mutex_init() for you. Also, you
> must always call pthread_mutex_destroy() to clean up, just the same as
> if you had called pthread_mutex_init() yourself.
I've made small corrections in test sample, so now mutex initialised
only once, and i've added pthread_mutex_destroy() function call. But
the problem still remains.
Here is two test applications - one of them uses API threads, and the
other pthreads. Program with pthreads don't have any leaks, while
program with API threads produces lots of them.
//program with handle leaks
#include <pthread.h>
#include <windows.h>
#include <conio.h>
pthread_mutex_t mutex(PTHREAD_RECURSIVE_MUTEX_INITIALIZER);
DWORD WINAPI threadProc(void *param)
{
pthread_mutex_lock(&mutex);
pthread_mutex_unlock(&mutex);
return 0;
}
void main()
{
const int max_threads = 500;
DWORD id;
HANDLE th[max_threads];
int i;
for (i=0;i<max_threads;i++)
th[i]=CreateThread(0,0,threadProc,0,0,&id);
for (i=0;i<max_threads;i++)
{
WaitForSingleObject(th[i],INFINITE);
CloseHandle(th[i]);
}
pthread_mutex_destroy(&mutex);
getch();
}
==========================
//program without handle leaks
#include <pthread.h>
#include <windows.h>
#include <conio.h>
pthread_mutex_t mutex(PTHREAD_RECURSIVE_MUTEX_INITIALIZER);
void* threadProc(void *param)
{
pthread_mutex_lock(&mutex);
pthread_mutex_unlock(&mutex);
return 0;
}
void main()
{
const int max_threads = 500;
DWORD id;
pthread_t th[max_threads];
int i;
for (i=0;i<max_threads;i++)
pthread_create(&(th[i]),0,threadProc,(void*)i);
for (i=0;i<max_threads;i++)
pthread_join(th[i],(void**)&id);
pthread_mutex_destroy(&mutex);
getch();
}
Best regards,
Dmitrii Sernii