Bug 98094

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Description of problem:
Threads fail to cancel at sem_wait()  on rh9, glibc 2.3.2-27.9.

The symptom is that the thread fails to join after it is cancelled on a
sem_wait(). If the example program is executed from bash and is suspended (via
ctrl-Z) and resumed (via a "fg"), it cancels correctly.

Code example supplied works on rh8.0 always, and rh9 under the following
circumstances:
1) Custom built kernel (stock linux 2.4.21 from kernel.org)
2) if the following environmental variable (and value) exists 
LD_ASSUME_KERNEL=2.4.19

The code fragment was compiled as fiollows: 
   gcc -Wall -ansi-pedantic pthreads-test.c -o pthreads-test -lpthread

------------------------------------ pthreads-test.c
-------------------------------------------------
#include <semaphore.h>
#include <pthread.h>
#include <stdio.h>
#include <unistd.h>

sem_t sem;


void *thread( void *stuff )
{
	while(1)
	{
		sem_wait(&sem);
		printf("Burp\n");
	}
}

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

	pthread_t t1;
	pthread_attr_t t1_attr;
	pthread_attr_init(&t1_attr);
	void *retval;
	
	pthread_attr_setdetachstate(&t1_attr, PTHREAD_CREATE_JOINABLE);

	sem_init(&sem,0,0);

	pthread_create(&t1,  &t1_attr, &thread, 0);

	/* Make sure the thread is waiting at the semaphore */
	sleep(1);
	
	sem_post(&sem);
	
	/* Must burp here and wait on the sem_wait in the thread */

	sleep(1);

	/* Thread must be at the semaphore now, so cancel it. */
	pthread_cancel(t1);
	printf("Waiting for thread to join\n");
	pthread_join(t1,&retval);

	/* If we don't get here, the thread did not cancel. Press ctrl-Z and
		type BG, and it will cancel then. Weird. */
	printf("OK. sem_wait() is a cancellation point.\n");

	return 0;

}
--------------------------------------------------------- end
---------------------------------------

Version-Release number of selected component (if applicable):
linux version 2.4.20-18.9

How reproducible:
Always

Steps to Reproduce:
1. Buiild code fragment in teh description and execute it
2. Note that it fails to report "OK. sem_wait() is a cancellation point"
3. If in bash, suspend using crtl-Z, and start using "fg". Note that it now cancells
    

Actual Results:  ./pthreads-test
Start
Burp


Expected Results:  ./pthreads-test
Burp
Waiting for thread to join
OK. sem_wait() is a cancellation point.


Additional info:

It is related to bugs 86416 and 89601. This report provides a small C program
that reproduces the problem.