From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kevin Hilman Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 6) Date: Fri, 14 May 2010 09:06:50 -0700 Message-ID: <878w7mpiw5.fsf@deeprootsystems.com> References: <20100513191717.GA3428@atomide.com> <20100513192522.GA19256@srcf.ucam.org> <20100513194205.GC3428@atomide.com> <20100513195349.GB19722@srcf.ucam.org> <20100513200003.GE3428@atomide.com> <20100513200814.GA20254@srcf.ucam.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: In-Reply-To: <20100513200814.GA20254@srcf.ucam.org> (Matthew Garrett's message of "Thu\, 13 May 2010 21\:08\:14 +0100") Sender: linux-kernel-owner@vger.kernel.org To: Matthew Garrett Cc: Tony Lindgren , Alan Stern , Paul Walmsley , Arve =?iso-8859-1?Q?Hj=F8nnev=E5g?= , Linux-pm mailing list , Kernel development list , Tejun Heo , Oleg Nesterov , magnus.damm@gmail.com, Theodore Ts'o , mark gross , Arjan van de Ven , Geoff Smith , Brian Swetland , "Rafael J. Wysocki" , =?iso-8859-1?Q?Beno=EEt?= Cousson , linux-omap@vger.kernel.org, Vitaly Wool , Mark Brown , Liam Girdwood List-Id: linux-omap@vger.kernel.org Matthew Garrett writes: > On Thu, May 13, 2010 at 01:00:04PM -0700, Tony Lindgren wrote: > >> The system stays running because there's something to do. The system >> won't suspend until all the processors hit the kernel idle loop and >> the next_timer_interrupt_critical() returns nothing. > > At which point an application in a busy loop cripples you. I think we > could implement your suggestion more easily by just giving untrusted > applications an effectively infinite amount of timer slack, > > but it still doesn't handle the case where an app behaves > excrutiatingly badly. Is design for exruciatingly bad apps a design requirement? If so, opportunistic suspend + suspend blockers fails as well. An app could easily hold a suspend blocker during its entire execution crippling PM. Using opportunistic suspend may possibly allow you contain bad apps/drivers, but at the cost of having to patch already working and trusted apps and known-working kernel code with suspend blockers. IMO, rather than accepting a solution that allows bad apps to run wild, it would be much better to _continue_ focus on tools for finding and containing bad apps. This approach has the added bonus of solving problems on *every* linux-based system, not just Android. Kevin