From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Andreas Schwab Newsgroups: gmane.emacs.devel Subject: Re: busyloop in sigchld_handler Date: Mon, 12 Mar 2007 19:45:03 +0100 Message-ID: References: <45F59395.4010708@gnu.org> NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable X-Trace: sea.gmane.org 1173725132 10631 80.91.229.12 (12 Mar 2007 18:45:32 GMT) X-Complaints-To: usenet@sea.gmane.org NNTP-Posting-Date: Mon, 12 Mar 2007 18:45:32 +0000 (UTC) Cc: emacs-devel@gnu.org To: Sam Steingold Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Mon Mar 12 19:45:26 2007 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([199.232.76.165]) by lo.gmane.org with esmtp (Exim 4.50) id 1HQpWP-0003X1-J0 for ged-emacs-devel@m.gmane.org; Mon, 12 Mar 2007 19:45:25 +0100 Original-Received: from localhost ([127.0.0.1] helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1HQpX5-0004ql-Tf for ged-emacs-devel@m.gmane.org; Mon, 12 Mar 2007 13:46:07 -0500 Original-Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1HQpWu-0004qg-8d for emacs-devel@gnu.org; Mon, 12 Mar 2007 14:45:56 -0400 Original-Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1HQpWs-0004qU-8D for emacs-devel@gnu.org; Mon, 12 Mar 2007 14:45:55 -0400 Original-Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1HQpWs-0004qR-1N for emacs-devel@gnu.org; Mon, 12 Mar 2007 13:45:54 -0500 Original-Received: from ns.suse.de ([195.135.220.2] helo=mx1.suse.de) by monty-python.gnu.org with esmtps (TLS-1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1HQpW6-0004dO-4G; Mon, 12 Mar 2007 14:45:06 -0400 Original-Received: from Relay1.suse.de (mail2.suse.de [195.135.221.8]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.suse.de (Postfix) with ESMTP id D1D931226A; Mon, 12 Mar 2007 19:45:03 +0100 (CET) X-Yow: It's the RINSE CYCLE!! They've ALL IGNORED the RINSE CYCLE!! In-Reply-To: <45F59395.4010708@gnu.org> (Sam Steingold's message of "Mon, 12 Mar 2007 13:53:25 -0400") User-Agent: Gnus/5.110006 (No Gnus v0.6) Emacs/22.0.91 (gnu/linux) X-detected-kernel: Linux 2.4-2.6 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.devel:67803 Archived-At: Sam Steingold writes: > Andreas Schwab wrote: >> Sam Steingold writes: >> >>> wait3 is a system call, which, when invoked in a loop, prevents the >>> kernel from doing anything else (in this case, sending SIGCHLD to >>> emacs). sleep allows the kernel some time to pass the signal. >> >> I don't find this explanation convincing at all. Since the system cal= l is >> made _inside_ the signal handler, the signal is actually blocked here,= so >> it cannot be delivered anyway. > > yes, you are right. > what I should have said was that by making a system call in a busyloop, > emacs prevents the kernel from doing what it needs to do to the the chi= ld > so that wait3 will succeed. What does the kernel have to do? The EINTR error will only happen when the system call was interrupted _and_ a signal handler was called. Andreas. --=20 Andreas Schwab, SuSE Labs, schwab@suse.de SuSE Linux Products GmbH, Maxfeldstra=DFe 5, 90409 N=FCrnberg, Germany PGP key fingerprint =3D 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED= 5 "And now for something completely different."