From owner-cvs-src@FreeBSD.ORG Wed Jul 14 19:29:59 2004 Return-Path: Delivered-To: cvs-src@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 8CB5016A4DB; Wed, 14 Jul 2004 19:29:59 +0000 (GMT) Received: from www.cryptography.com (li-22.members.linode.com [64.5.53.22]) by mx1.FreeBSD.org (Postfix) with ESMTP id 025BF43D66; Wed, 14 Jul 2004 19:29:59 +0000 (GMT) (envelope-from nate@root.org) Received: from [10.0.0.34] (adsl-63-195-111-154.dsl.snfc21.pacbell.net [63.195.111.154]) by www.cryptography.com (8.12.8/8.12.8) with ESMTP id i6EJTvrb018916 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT); Wed, 14 Jul 2004 12:29:58 -0700 Message-ID: <40F5897C.7010904@root.org> Date: Wed, 14 Jul 2004 12:29:00 -0700 From: Nate Lawson User-Agent: Mozilla Thunderbird 0.7.1 (Windows/20040626) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Alfred Perlstein References: <200407142001.25615.dfr@nlsystems.com> <20040714191118.GF95729@elvis.mu.org> In-Reply-To: <20040714191118.GF95729@elvis.mu.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit cc: Robert Watson cc: src-committers@freebsd.org cc: Doug Rabson cc: cvs-all@freebsd.org cc: cvs-src@freebsd.org Subject: Re: cvs commit: src/sys/kern kern_event.c src/sys/sys eventvar.h X-BeenThere: cvs-src@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: CVS commit messages for the src tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 14 Jul 2004 19:29:59 -0000 Alfred Perlstein wrote: > * Doug Rabson [040714 12:01] wrote: >>On Wednesday 14 July 2004 19:56, Robert Watson wrote: >>>On Wed, 14 Jul 2004, Alfred Perlstein wrote: >>>>I can fix this by setting a "sigio in progress" on the kqeue and >>>>not calling pgsigio() while one is in progress. >>> >>>My worry is the inter-subsystem calling. We often call KNOTE() while >>>holding existing locks in the calling subsystem that we can't drop. >>>Generally, kqueue is a leaf node subsystem in that it's called from >>>many places under many circumstances, and needs to not disrupt the >>>calling state by doing "weird things". What's there before your >>>change is not too disruptive/weird; afterwards, we call into the body >>>of the process signalling code which requires additional process >>>locks. Note that there are other paths to the same suffering: if any >>>other signal is delivered to a process that's monitoring for signals >>>with kqueue causing a sigio, you're still recursing into the signal >>>subsystem. >> >>Seems to me that the best thing to do is to defer the psigio() to a >>taskqueue that will run in a simpler locking environment. > > I was thinking that, but I'm worried about "stale delivery", > perhaps we need to record the generation count (process start time) > in the sigio as well as the request sent, so that we don't send > a signal to the wrong process. Sorry, never mind my previous comments. I was recently working with kqueue AIO notifications and misread AIO for kqueue. Oops. -- -Nate