From owner-freebsd-hackers@freebsd.org  Mon Nov 21 14:16:22 2016
Return-Path: <owner-freebsd-hackers@freebsd.org>
Delivered-To: freebsd-hackers@mailman.ysv.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 by mailman.ysv.freebsd.org (Postfix) with ESMTP id C1FE9C4C115
 for <freebsd-hackers@mailman.ysv.freebsd.org>;
 Mon, 21 Nov 2016 14:16:22 +0000 (UTC)
 (envelope-from Volker.Lendecke@SerNet.DE)
Received: from mail.SerNet.de (mail1.SerNet.de [193.175.80.2])
 (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits))
 (Client did not present a certificate)
 by mx1.freebsd.org (Postfix) with ESMTPS id 8C5B71DB7
 for <freebsd-hackers@freebsd.org>; Mon, 21 Nov 2016 14:16:21 +0000 (UTC)
 (envelope-from Volker.Lendecke@SerNet.DE)
Received: from intern.SerNet.DE by mail.SerNet.DE with esmtps (Exim 4.84_2 #1)
 id 1c8pOM-0001KM-Mq; Mon, 21 Nov 2016 15:16:18 +0100
Received: by intern.sernet.de
 id 1c8pOM-0004gu-K9; Mon, 21 Nov 2016 15:16:18 +0100
Date: Mon, 21 Nov 2016 15:16:16 +0100
From: Volker Lendecke <Volker.Lendecke@SerNet.DE>
To: Konstantin Belousov <kostikbel@gmail.com>
Cc: freebsd-hackers@freebsd.org
Subject: Re: process shared mutexes?
Message-ID: <20161121141616.GB30947@sernet.de>
Reply-To: Volker.Lendecke@SerNet.DE
References: <20161121133528.GA30947@sernet.de>
 <20161121135036.GY54029@kib.kiev.ua>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20161121135036.GY54029@kib.kiev.ua>
User-Agent: Mutt/1.5.23 (2014-03-12)
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.23
Precedence: list
List-Id: Technical Discussions relating to FreeBSD
 <freebsd-hackers.freebsd.org>
List-Unsubscribe: <https://lists.freebsd.org/mailman/options/freebsd-hackers>, 
 <mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers/>
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <https://lists.freebsd.org/mailman/listinfo/freebsd-hackers>, 
 <mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 21 Nov 2016 14:16:22 -0000

On Mon, Nov 21, 2016 at 03:50:36PM +0200, Konstantin Belousov wrote:
> On Mon, Nov 21, 2016 at 02:35:28PM +0100, Volker Lendecke wrote:
> > Hello!
> > 
> > For Samba's tdb I'm trying to get process shared robust mutexes to
> > work. However, tdb has a usage pattern that seems to confuse FreeBSD
> > 11 (32-bit x86 if that matters).
> > 
> > The attached program fails in the final pthread_mutex_lock call. If I
> > comment out the call to
> > 
> > ptr = mmap(NULL, 0xb0, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0x1000);
> > 
> > it works.
> > 
> > FWIW, tdb uses robust shared mutexes on Linux successfully for a while
> > now. I haven't tried Solaris yet, the only other platform I know about
> > that has them.
> > 
> > What am I doing wrong?
> > 
> > Thanks,
> > 
> 
> There is no attached program, please mail it either inline or put it
> somewhere on web.

Hmm. Inline now.

Volker


#include <stdio.h>
#include <pthread.h>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <string.h>

int main(int argc, const char *argv[])
{
	int fd, ret;
	void *ptr;
	pthread_mutex_t *m;
	pthread_mutexattr_t attr;

	if (argc != 2) {
		fprintf(stderr, "usage: %s <filename>\n", argv[0]);
		return 1;
	}

	fd = open(argv[1], O_RDWR|O_CREAT, 0644);
	if (fd == -1) {
		perror("open failed");
		return 1;
	}

	ret = ftruncate(fd, 0x1000+0xb0);
	if (ret == -1) {
		perror("ftruncate failed");
		return 1;
	}

	m = mmap(NULL, 0x1000, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
	if (m == MAP_FAILED) {
		perror("mmap failed");
		return 1;
	}

	ret = pthread_mutexattr_init(&attr);
	if (ret != 0) {
		fprintf(stderr, "pthread_mutexattr_init failed: %s\n",
			strerror(ret));
		return 1;
	}

	ret = pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_SHARED);
	if (ret != 0) {
		fprintf(stderr, "pthread_mutexattr_setpshared failed: %s\n",
			strerror(ret));
		return 1;
	}

	ret = pthread_mutex_init(m, &attr);
	if (ret != 0) {
		fprintf(stderr, "pthread_mutex_init failed: %s\n",
			strerror(ret));
		return 1;
	}

	ret = munmap(m, 0x1000);
	if (ret == -1) {
		perror("munmap failed");
		return 1;
	}

#if 1
	ptr = mmap(NULL, 0xb0, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0x1000);
	if (ptr == MAP_FAILED) {
		perror("mmap failed");
		return 1;
	}
#endif

	m = mmap(NULL, 0x1000, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
	if (m == MAP_FAILED) {
		perror("mmap failed");
		return 1;
	}

	ret = pthread_mutex_lock(m);
	if (ret != 0) {
		fprintf(stderr, "pthread_mutex_lock failed: %s\n",
			strerror(ret));
		return 1;
	}

	ret = pthread_mutex_unlock(m);
	if (ret != 0) {
		fprintf(stderr, "pthread_mutex_lock failed: %s\n",
			strerror(ret));
		return 1;
	}

	return 0;
}