From owner-freebsd-bugs@FreeBSD.ORG  Sun Nov 18 17:23:53 2007
Return-Path: <owner-freebsd-bugs@FreeBSD.ORG>
Delivered-To: freebsd-bugs@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 50EB716A494
	for <freebsd-bugs@freebsd.org>; Sun, 18 Nov 2007 17:23:53 +0000 (UTC)
	(envelope-from shcheklein@gmail.com)
Received: from nz-out-0506.google.com (nz-out-0506.google.com [64.233.162.238])
	by mx1.freebsd.org (Postfix) with ESMTP id 0F27813C457
	for <freebsd-bugs@freebsd.org>; Sun, 18 Nov 2007 17:23:52 +0000 (UTC)
	(envelope-from shcheklein@gmail.com)
Received: by nz-out-0506.google.com with SMTP id l8so1105360nzf
	for <freebsd-bugs@freebsd.org>; Sun, 18 Nov 2007 09:23:45 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=beta;
	h=domainkey-signature:received:received:message-id:date:from:to:subject:mime-version:content-type;
	bh=1R6+3tb6mCzyijIyGfXgzDm5PAgKWrvwA9D1+NyaqTs=;
	b=fPzNqnA6GsUrPhUXmdv9WRr2bCAk18YDq2BVdmVNHogmcYm9wzDPkxoKxaYjC+YahpQPTO9QIwtrXDymKnDC8l0pEpZabeirAfni6l0IIMMjXUV9owv9XtfN5a9VhEYSdzN+1/mo3q6jA8dlQu02DEaFBxiwOPtKlQaGQ6TP7WY=
DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta;
	h=received:message-id:date:from:to:subject:mime-version:content-type;
	b=pEJZanxZh9BCS2ac2QosAySPTSBsoVb15MmRSAHiWTyTnB7d93mpRcfo/s4UNinL0yV2sIod1GVkNqVf6t54MsAejexb0/0WytU7n3ewUFWF/GGd8Cmhh6Woz9Hur7v7DtavjIOeRYFUGqUyDS1eHfvm8BD8pZBhnuIz/nBLmgc=
Received: by 10.142.212.19 with SMTP id k19mr913687wfg.1195405169126;
	Sun, 18 Nov 2007 08:59:29 -0800 (PST)
Received: by 10.142.52.2 with HTTP; Sun, 18 Nov 2007 08:59:29 -0800 (PST)
Message-ID: <3034886f0711180859r1c9d8c17n82d2f89158197d9b@mail.gmail.com>
Date: Sun, 18 Nov 2007 19:59:29 +0300
From: "Ivan Shcheklein" <shcheklein@gmail.com>
To: freebsd-bugs@freebsd.org
MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
X-Content-Filtered-By: Mailman/MimeDel 2.1.5
Subject: Bug in semop() in multiprocess environment?
X-BeenThere: freebsd-bugs@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Bug reports <freebsd-bugs.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-bugs>,
	<mailto:freebsd-bugs-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-bugs>
List-Post: <mailto:freebsd-bugs@freebsd.org>
List-Help: <mailto:freebsd-bugs-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-bugs>,
	<mailto:freebsd-bugs-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sun, 18 Nov 2007 17:23:53 -0000

Hi All,

It seems to me that there is a bug in the semop() code:

After wakeup we see the following:

        /*
         * The semaphore is still alive.  Readjust the count of
         * waiting processes.
         */
        if (sopptr->sem_op == 0)
            semptr->semzcnt--;
        else
            semptr->semncnt--;

It seems to me that "semptr" can be invalid after wakeup. For example,
semaphore's base can be changed after remove called on another previously
created semaphore.

I think semptr must be renewed after wakeup.

Ivan Shcheklein