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Date: Thu, 25 Aug 2011 17:39:00 -0700
From: David Rothenberger <daveroth AT acm DOT org>
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To: cygwin <cygwin AT cygwin DOT com>
Subject: STC for libapr1 failure
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For a while now, the test cases that come with libapr1 have been
bombing with this message:

  *** fatal error - NtCreateEvent(lock): 0xC0000035

I finally took some time to investigate and have extracted a STC
that demonstrates the problem.

It's been a decade since I did any C programming, so I'm not really
sure that the STC is valid. However, it does work on my Debian
box. (I know that doesn't really mean anything, but it's the best I
can do.)

I've tried this on my Win7-64 box running the 20110822 snapshot and
on a WinXP VM running 1.7.9. I get the same results in both places.

Regards,
David

-- 
David Rothenberger  ----  daveroth AT acm DOT org

The First Rule of Program Optimization:
        Don't do it.

The Second Rule of Program Optimization (for experts only!):
        Don't do it yet.
                -- Michael Jackson

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/***********************************************************************
 * This is a STC that causes the following error on my test machine:
 *   NtCreateEvent(lock): 0xC0000035
 *
 * It tries to use flock() for file locking. It creates a temporary
 * file, the uses fork to spawn a number of children. Each child opens
 * the file, then repeatedly uses flock to lock and unlock it.
 *
 * This test was extracted from the APR test suite.
 *
 * Compile: gcc -Wall -o stc-flock-fork stc-flock-fork.c
 ***********************************************************************/

#include <sys/types.h>
#include <sys/file.h>
#include <sys/wait.h>

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>

#define MAX_ITER 2000
#define CHILDREN 6

/* A temporary file used for flock. */
char tmpfilename[] = "/tmp/flocktstXXXXXX";

/* Fork and use flock to lock and unlock the file repeatedly in the child. */
void make_child(int trylock, pid_t *pid)
{
    if ((*pid = fork()) < 0) {
        perror("fork failed");
        exit(1);
    }
    else if (*pid == 0) {
        int fd2 = open(tmpfilename, O_RDONLY);
        if (fd2 < 0) {
            perror("child open");
            exit(1);
        }

        int rc;
        int i;
        for (i=0; i<MAX_ITER; ++i) {
            do {
                rc = flock(fd2, LOCK_EX);
            } while (rc < 0 && errno == EINTR);
            if (rc < 0) {
                perror("lock");
                exit(1);
            }
            
            do {
                rc = flock(fd2, LOCK_UN);
            } while (rc < 0 && errno == EINTR);
            if (rc < 0) {
                perror("unlock");
                exit(1);
            }
        }
        exit(0);
    }
}

/* Wait for the child to finish. */
void await_child(pid_t pid)
{
    pid_t pstatus;
    int exit_int;

    do {
        pstatus = waitpid(pid, &exit_int, WUNTRACED);
    } while (pstatus < 0 && errno == EINTR);
}

int main(int argc, const char * const * argv, const char * const *env)
{
    pid_t child[CHILDREN];
    int n;
    int fd;
 
    /* Create the temporary file. */
    fd = mkstemp(tmpfilename);
    if (fd < 0) {
        perror("open failed");
        exit(1);
    }
    close(fd);

    /* Create the children. */
    for (n = 0; n < CHILDREN; n++)
        make_child(0, &child[n]);

    /* Wait for them to finish. */
    for (n = 0; n < CHILDREN; n++)
        await_child(child[n]);

    /* Clean up. */
    unlink(tmpfilename);
    return 0;
}


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