From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: Re: Re: [PATCH] Remove process freezer from suspend to RAM pathway Date: Fri, 06 Jul 2007 08:59:52 +1000 Message-ID: <1183676393.3388.89.camel@localhost.localdomain> References: Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-pm-bounces@lists.linux-foundation.org Errors-To: linux-pm-bounces@lists.linux-foundation.org To: Alan Stern Cc: Matthew Garrett , Kernel development list , Pavel Machek , Johannes Berg , Linux-pm mailing list List-Id: linux-pm@vger.kernel.org On Thu, 2007-07-05 at 10:23 -0400, Alan Stern wrote: > > How will that help? Block the kernel thread in the freezer or block it > in the driver -- either way it is blocked. So how do your deadlocks > get resolved? Because nobody is waiting on that kernel thread anyway without a freezer so there is no deadlock anymore. > I disagree with your analysis -- not that it's completely wrong, but it > points out an existing basic problem in the kernel. The kernel should > never depend on userspace! More correctly, a task executing in the > kernel should never block with any sort of mutex or other lock held (in > a way that would preclude it from being frozen, let's say) while > waiting for a response from userspace. > > Then the dependency graph would be easy to construct: User tasks can > depend on whatever they want, and kernel threads never depend on a user > task. In an idea world, there would be no hunger... > If this contradicts the existing implementations and APIs for userspace > filesystems, then so be it. My conclusion would be that the > implementations and APIs should be changed. Why are you guys working so hard and spending so much energy to try to avoid doing the right thing is beyond my understanding... > It _does_ apply to kernel threads. That's exactly why I wrote above > that kernel threads which try to do I/O during a suspend will need > extra attention. Ok none at all if you don't have a freezer. Ben.