From owner-cvs-all@FreeBSD.ORG Wed May 31 14:50:29 2006 Return-Path: X-Original-To: cvs-all@freebsd.org Delivered-To: cvs-all@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 66EB816B122; Wed, 31 May 2006 14:50:29 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from server.baldwin.cx (66-23-211-162.clients.speedfactory.net [66.23.211.162]) by mx1.FreeBSD.org (Postfix) with ESMTP id A3FC443D48; Wed, 31 May 2006 14:50:26 +0000 (GMT) (envelope-from jhb@freebsd.org) Received: from [131.106.61.215] (72-255-64-170.client.stsn.net [72.255.64.170]) (authenticated bits=0) by server.baldwin.cx (8.13.4/8.13.4) with ESMTP id k4VEoL84068255; Wed, 31 May 2006 10:50:25 -0400 (EDT) (envelope-from jhb@freebsd.org) From: John Baldwin To: Scott Long Date: Wed, 31 May 2006 10:50:11 -0400 User-Agent: KMail/1.9.1 References: <200605252306.k4PN6cCS081708@repoman.freebsd.org> <44766F75.9060100@samsco.org> In-Reply-To: <44766F75.9060100@samsco.org> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200605311050.12156.jhb@freebsd.org> X-Virus-Scanned: ClamAV 0.87.1/1501/Wed May 31 06:23:26 2006 on server.baldwin.cx X-Virus-Status: Clean X-Spam-Status: No, score=-4.2 required=4.2 tests=ALL_TRUSTED,AWL,BAYES_00 autolearn=ham version=3.1.0 X-Spam-Checker-Version: SpamAssassin 3.1.0 (2005-09-13) on server.baldwin.cx Cc: cvs-src@freebsd.org, src-committers@freebsd.org, Warner Losh , cvs-all@freebsd.org Subject: Re: cvs commit: src/sys/dev/syscons/apm apm_saver.c src/sys/i386/bios apm.c apm.h X-BeenThere: cvs-all@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: CVS commit messages for the entire tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 31 May 2006 14:50:33 -0000 On Thursday 25 May 2006 23:01, Scott Long wrote: > Warner Losh wrote: > > > imp 2006-05-25 23:06:38 UTC > > > > FreeBSD src repository > > > > Modified files: > > sys/dev/syscons/apm apm_saver.c > > sys/i386/bios apm.c apm.h > > Log: > > APM was calling the suspend process from a timeout. This meant that > > other timeouts could not happen while suspending, including timeouts > > for things like msleep. This caused the system to hang on suspend > > when the cbb was enabled, since its suspend path powered down the > > socket which used a timeout to wait for it to be done. > > > > APM now creates a thread when it is enabled, and deletes the thread > > when it is disabled. This thread takes the place of the timeout by > > doing its polling every ~.9s. When the thread is disabled, it will > > wakeup early, otherwise it times out and polls the varius things the > > old timeout polled (APM events, suspend delays, etc). > > > > This makes my Sony VAIO 505TS suspend/resume correctly when APM is > > enabled (ACPI is black listed on my 505TS). > > > > This will likely fix other problems with the suspend path where > > drivers would sleep with msleep and/or do other timeouts. Maybe > > there's some special case code that would use DELAY while suspending > > and msleep otherwise that can be revisited and removed. > > > > This was also tested by glebius@, who pointed out that in the patch I > > sent him, I'd forgotten apm_saver.c > > > > MFC After: 3 weeks > > In the past, I've been against mandating that callouts/timeouts/generic > taskqueues should not be allowed to sleep. However, after looking over > the history of this problem as well as others, it seems that it's just > too easy for driver authors to make bad assumptions and wind up with a > priority inversion/deadlock like this. It would be relatively trivial > to mark these contexts as being non-sleepable and have the msleep code > enforce it, like is done with ithreads. What do you think? Anyways, > thanks for looking at this and fixing it. We already do for timeouts if INVARIANTS is on: softclock() { ... THREAD_NO_SLEEPING(); c_func(c_arg); THREAD_SLEEPING_OK(); ... } That has been in place since 6.0 IIRC. -- John Baldwin