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Date: Fri, 29 Jul 2011 16:59:00 -0000
Message-ID: <CADqjQ-JDwMxofjUJ0izOhyAaen61bmmG7UgWXwk-22ifcdF1AA@mail.gmail.com>
Subject: Pthread error?
From: Jan Chludzinski <jan.chludzinski@gmail.com>
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The code below appears to have incorrect behavior.=A0 The output is:

$ ./a.exe
Enter Testcase - ./a
Create/start threads
Thread 009e0290 00000000: Entered
Thread 009f0320 00000000: Entered
Thread 009f03a8 00000000: Entered
Thread 18dbce64 00000000: INITIALIZE RESOURCE
Wait for the threads to complete, and release their resources
Thread 009f0430 00000000: Entered
Thread 00a104f8 00000000: Entered
Thread 009e0290 00000001: resource is>>> 0
Thread 009e0290 0000002a: The resource is 0
Thread 009f0320 0000002a: The resource is 0
Thread 009f03a8 0000002a: The resource is 0
Thread 009f0430 0000002a: The resource is 0
Thread 00a104f8 0000002a: The resource is 0
Main completed

If I understand pthread_once(...) correctly, the output should be:

Thread ... ...: The resource is 42

for all threads.=A0 The really strange thing is the printf(...) in
initFunction().=A0 This should print "resource is>>> 42" but I get:
"resource is>>> 0".

What's up?

I'm using Cygwin 1.7 on Windows 7 with gcc (GCC) 4.3.4 20090804 (release) 1.

---John


///////////////////////////////////////////////////////////////////////////=
/////////////////////////////

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#define checkResults(string, val) {=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 \
=A0if (val) {=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 \
=A0=A0 printf("Failed with %d at %s", val, string); \
=A0=A0 exit(1);=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 \
=A0}=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 \
}

#define=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 NUMTHREADS=A0=A0 5
pthread_once_t=A0=A0=A0=A0=A0=A0=A0=A0=A0 oneTimeInit =3D PTHREAD_ONCE_INIT;
int=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 initialized=
 =3D 0;
int=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 resource=A0=
=A0=A0 =3D 0;

void initFunction(void)
{
=A0=A0 printf("Thread %.8x %.8x: INITIALIZE RESOURCE\n");
=A0=A0 initialized =3D 1;
=A0=A0 resource =3D 42;
=A0=A0 printf("Thread %.8x %.8x: resource is>>> %d\n",
=A0=A0=A0 =A0pthread_self(), resource);
}

void *theThread(void *parm)
{
=A0 int=A0=A0 rc;
=A0 printf("Thread %.8x %.8x: Entered\n", pthread_self());
=A0 //if (!initialized) {
=A0=A0=A0 rc =3D pthread_once(&oneTimeInit, initFunction);
=A0=A0=A0 checkResults("pthread_once()\n", rc);
=A0=A0=A0 //}
=A0 printf("Thread %.8x %.8x: The resource is %d\n",
=A0=A0=A0 =A0pthread_self(), resource);
=A0 return NULL;
}

int main(int argc, char **argv)
{
=A0 pthread_t=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 thread[NUMTHREADS];
=A0 int=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 rc=3D0;
=A0 int=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 i;

=A0 printf("Enter Testcase - %s\n", argv[0]);

=A0 printf("Create/start threads\n");
=A0 for (i=3D0; i <NUMTHREADS; ++i) {
=A0=A0=A0 rc =3D pthread_create(&thread[i], NULL, theThread, NULL);
=A0=A0=A0 checkResults("pthread_create()\n", rc);
=A0 }

=A0 printf("Wait for the threads to complete, and release their resources\n=
");
=A0 for (i=3D0; i <NUMTHREADS; ++i) {
=A0=A0=A0 rc =3D pthread_join(thread[i], NULL);
=A0=A0=A0 checkResults("pthread_join()\n", rc);
=A0 }

=A0 printf("Main completed\n");
=A0 return 0;
}

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