X-Recipient: archive-cygwin AT delorie DOT com
X-Spam-Check-By: sourceware.org
Date: Fri, 18 Sep 2009 17:35:22 -0400
From: Christopher Faylor <cgf-use-the-mailinglist-please AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: [1.7] sigwait bug (SIGCHLD delayed to a next regular signal)
Message-ID: <20090918213522.GA12527@ednor.casa.cgf.cx>
Reply-To: cygwin AT cygwin DOT com
Mail-Followup-To: cygwin AT cygwin DOT com
References: <loom DOT 20090918T184921-716 AT post DOT gmane DOT org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <loom.20090918T184921-716@post.gmane.org>
User-Agent: Mutt/1.5.20 (2009-06-14)
Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm
Precedence: bulk
List-Id: <cygwin.cygwin.com>
List-Unsubscribe: <mailto:cygwin-unsubscribe-archive-cygwin=delorie DOT com AT cygwin DOT com>
List-Subscribe: <mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive: <http://sourceware.org/ml/cygwin/>
List-Post: <mailto:cygwin AT cygwin DOT com>
List-Help: <mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender: cygwin-owner AT cygwin DOT com
Mail-Followup-To: cygwin AT cygwin DOT com
Delivered-To: mailing list cygwin AT cygwin DOT com

On Fri, Sep 18, 2009 at 04:57:56PM +0000, Waldemar Rachwal wrote:
>A problem seems very close to one described in
>http://sourceware.org/ml/cygwin/2009-08/msg00797.html
>and now I don't think it can be easily explained by
>"limitation in Cygwin's implementation of SIGWINCH".
>
>What I did this time...
>
>When I fork children and next observe their termination in
>the parent process by means of sigwait(),
>*none* of the SIGCHLD signals is returned immediately until some other
>"regular" signal, let's say SIGINT, is sent to the parent.
>
>Apparently, signals like SIGWINCH and SIGCHLD, which are a little bit
>special, need to be kicked by other signal to be eventually returned by
>sigwait().
>What makes these signals "special" is that their default action is `to
>IGNORE' and to be useful for sigwait() they need to register some dummy
>handler.
>Maybe this has something to do why sigwait() doesn't work as
>expected.

Thanks for the test case.  The problem has nothing to do with anything
"special" about SIGCHLD.  It's a signal like any other signal.

Cygwin was not performing sigwait() processing if there was a handler
set up for the signal.  Your test case would have worked if you had not
set up a dummy handler.

This will be fixed in the next snapshot.

cgf

--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple