From: David Rothenberger <daveroth@acm.org>
To: cygwin@cygwin.com
Subject: Re: STC for libapr1 failure
Date: Sat, 27 Aug 2011 22:27:00 -0000 [thread overview]
Message-ID: <4E596F50.3050205@acm.org> (raw)
In-Reply-To: <20110827203706.GA15411@calimero.vinschen.de>
[-- Attachment #1: Type: text/plain, Size: 1469 bytes --]
On 8/27/2011 1:37 PM, Corinna Vinschen wrote:
> On Aug 26 13:15, Corinna Vinschen wrote:
>> On Aug 25 17:39, David Rothenberger wrote:
>>> 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.
>>
>> Thanks a lot for the testcase. In theory, the NtCreateEvent call should
>> not have happened at all, since it's called under lock, and the code
>> around that should have made sure that the object doesn't exist at the
>> time.
>>
>> After a few hours of extrem puzzlement, I now finally know what happens.
>> It's kinda hard to explain.
>>
[... very good description of flock problem ...]
>
> Please test the latest snapshot. It should fix this problem, as well as
> a starvation problem with signals (and, fwiw, thread cancel events) in
> flock, lockf, and POSIX fcntl locks.
The new snapshot runs the flock STC. Thanks!
I've been building libapr1 without F_SETLK support for a while since
it was also triggering the "NtCreateEvent(lock): 0xC0000035"
error. Since you mentioned fcntl, I tried re-enabling the fcntl
mutexes. They still trigger the error.
I've attached a similar STC that uses fcntl instead of flock.
--
David Rothenberger ---- daveroth@acm.org
"It's what you learn after you know it all that counts."
-- John Wooden
[-- Attachment #2: stc-fcntl-fork.c --]
[-- Type: text/plain, Size: 3254 bytes --]
/***********************************************************************
* This is a STC that causes the following error on my test machine:
* NtCreateEvent(lock): 0xC0000035
*
* It tries to use fcntl() 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 fcntl to lock and unlock it.
*
* This test was extracted from the APR test suite.
*
* Compile: gcc -Wall -o stc-fcntl-fork stc-fcntl-fork.c
***********************************************************************/
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/wait.h>
#include <sys/file.h>
#define MAX_ITER 2000
#define CHILDREN 6
/* A temporary file used for fcntl. */
char tmpfilename[] = "/tmp/fcntlXXXXXX";
struct flock mutex_lock_it;
struct flock mutex_unlock_it;
/* Fork and use fcntl 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_RDWR);
if (fd2 < 0) {
perror("child open");
exit(1);
}
int rc;
int i;
for (i=0; i<MAX_ITER; ++i) {
do {
rc = fcntl(fd2, F_SETLKW, &mutex_lock_it);
} while (rc < 0 && errno == EINTR);
if (rc < 0) {
perror("lock");
exit(1);
}
do {
rc = fcntl(fd2, F_SETLKW, &mutex_unlock_it);
} 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);
/* Setup mutexes */
mutex_lock_it.l_whence = SEEK_SET; /* from current point */
mutex_lock_it.l_start = 0; /* -"- */
mutex_lock_it.l_len = 0; /* until end of file */
mutex_lock_it.l_type = F_WRLCK; /* set exclusive/write lock */
mutex_lock_it.l_pid = 0; /* pid not actually interesting */
mutex_unlock_it.l_whence = SEEK_SET; /* from current point */
mutex_unlock_it.l_start = 0; /* -"- */
mutex_unlock_it.l_len = 0; /* until end of file */
mutex_unlock_it.l_type = F_UNLCK; /* set exclusive/write lock */
mutex_unlock_it.l_pid = 0; /* pid not actually interesting */
/* 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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next prev parent reply other threads:[~2011-08-27 22:27 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-26 0:39 David Rothenberger
2011-08-26 11:16 ` Corinna Vinschen
2011-08-27 20:37 ` Corinna Vinschen
2011-08-27 22:27 ` David Rothenberger [this message]
2011-08-29 13:55 ` Corinna Vinschen
2011-08-29 17:09 ` David Rothenberger
2012-02-14 8:00 David Rothenberger
2012-02-14 8:07 ` David Rothenberger
2012-02-14 14:03 ` Corinna Vinschen
2012-02-14 14:46 ` Corinna Vinschen
2012-02-14 17:58 ` David Rothenberger
2012-02-14 18:25 ` Corinna Vinschen
2012-02-14 21:43 ` David Rothenberger
2012-02-15 15:39 ` Corinna Vinschen
2012-02-15 19:39 ` David Rothenberger
2012-02-15 20:46 ` Corinna Vinschen
2012-02-15 21:16 ` David Rothenberger
2012-02-15 21:20 ` Corinna Vinschen
2012-02-15 22:14 ` David Rothenberger
2012-02-16 14:11 ` Corinna Vinschen
2012-02-16 15:57 ` David Rothenberger
2012-02-16 16:06 ` Corinna Vinschen
2012-02-18 21:52 ` David Rothenberger
2012-02-20 14:19 ` Corinna Vinschen
2012-02-20 20:15 ` David Rothenberger
2012-02-21 1:29 ` Yaakov (Cygwin/X)
2012-02-21 8:59 ` Corinna Vinschen
2012-02-21 17:10 ` Corinna Vinschen
2012-02-23 14:20 ` Corinna Vinschen
2012-02-23 18:43 ` Achim Gratz
2012-02-24 3:49 ` Yaakov (Cygwin/X)
2012-02-24 8:15 ` Corinna Vinschen
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