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References: <44f83c19cc33e4382680fe3758164ccf AT rehley DOT net> <20050527202823 DOT GB4939 AT trixie DOT casa DOT cgf DOT cx> <0833be552ca5aa00a72ecef822250580 AT rehley DOT net> <20050528161515 DOT GA1323 AT trixie DOT casa DOT cgf DOT cx>
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From: Peter Rehley <peter AT rehley DOT net>
Subject: Re: pthreads, cygwin and pthread_mutex_lock not blocking
Date: Tue, 31 May 2005 10:15:27 -0700
To: cygwin AT cygwin DOT com
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Well, here is a simple test case, but turns out I wasn't using the=20
latest version.  I was having the problem on 1.5.12,  I haven't been=20
able to get a good build with cygwin 1.5.17-1.  It builds and I can run=20
the install script, but when I put the dll in place I see the message=20
"cygheap magic number mismatch detected", and gcc doesn't want to work.

I followed the instructions on the FAQ page for building cygwin.  Also=20
the only line that I changed was in winsup/cygwin/include/pthread.h,=20
line 56

from
#define PTHREAD_MUTEX_DEFAULT PTHREAD_MUTEX_ERRORCHECK
to
#define PTHREAD_MUTEX_DEFAULT PTHREAD_MUTEX_NORMAL

On the unmodified cygwin 1.5.17, the parent lock returns 45 (EDEADLK)

On May 28, 2005, at 9:15 AM, Christopher Faylor wrote:

> On Fri, May 27, 2005 at 04:35:39PM -0700, Peter Rehley wrote:
>> On May 27, 2005, at 1:28 PM, Christopher Faylor wrote:
>>
>>> On Fri, May 27, 2005 at 10:57:34AM -0700, Peter Rehley wrote:
>>>> I'm trying to use pthread in cygwin, and I'm expecting the function
>>>> pthread_mutex_lock to block when used.  However it is returning=20
>>>> error
>>>> 45 (EDEADLK).    I'm using a static initializer for the thread so=20
>>>> the
>>>> mutex is type PTHREAD_MUTEX_DEFAULT.
>>>> When I look through the pthread code I see that=20
>>>> PTHREAD_MUTEX_DEFAULT
>>>> is set to PTHREAD_MUTEX_ERRORCHECK,
>>>> When I do the same on linux or soloris, the pthread_mutex_lock=20
>>>> blocks,
>>>> and looking in the pthread.h file on those systems see that  the
>>>> default is set to PTHREAD_MUTEX_NORMAL.
>>>>
>>>> Why is cygwin using PTHREAD_MUTEX_ERRORCHECK as the default?  And=20
>>>> what
>>>> problems might occur if PTHREAD_MUTEX_DEFAULT is set to
>>>> PTHREAD_MUTEX_NORMAL?
>>>
>>> Why not just try it and report the results?
>> Done.  Hangs at WaitForSingleObject.
>
> Can you provide a STC(tm) (simple test case) which demonstrates the
> problem both with and without PTHREAD_MUTEX_ERRORCHECK?
>
> cgf
>
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>
>
Enjoy,
Peter
-------------------------------
A M=F8=F8se once bit my sister

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#include <stdio.h>
#include <signal.h>
#include <pthread.h>

pthread_mutex_t mutex;

void signal_rec(int sig_num)
  {
  printf("The child is done\n");
  pthread_mutex_unlock(&mutex);
  }

int main(int argc, char *argv[])
  {
  int ret_value;

  signal(SIGCHLD, signal_rec);

  mutex=PTHREAD_MUTEX_INITIALIZER;
  ret_value=pthread_mutex_lock(&mutex);
  printf("thread locked %d\n",ret_value);
  ret_value=fork();
  if (ret_value==0)
    {
    printf("I'm the child\n");
    sleep(5);
    printf("ahh, what a good nap\n");
    }
  else
    {
    printf("I'm the parent\n");
//    sleep(10);
    ret_value = pthread_mutex_lock(&mutex);
    printf("heh, I'm done %d\n",ret_value);
    }

  return 0;
  }

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