From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Garrett Subject: Re: [PATCH] Remove process freezer from suspend to RAM pathway Date: Tue, 3 Jul 2007 20:42:47 +0100 Message-ID: <20070703194247.GB27098@srcf.ucam.org> References: <20070703170233.GA25129@srcf.ucam.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline 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: linux-pm@lists.linux-foundation.org, linux-kernel@vger.kernel.org List-Id: linux-pm@vger.kernel.org On Tue, Jul 03, 2007 at 03:33:40PM -0400, Alan Stern wrote: > On Tue, 3 Jul 2007, Matthew Garrett wrote: > > > On Tue, Jul 03, 2007 at 12:57:17PM -0400, Alan Stern wrote: > > > On Tue, 3 Jul 2007, Matthew Garrett wrote: > > > > For the suspend to RAM case, that sounds absolutely fine. > > > > > > It's not so good when your suspend process has to wait for the call to > > > complete! > > > > Why would it have to? Sorry, I suspect I'm missing something obvious > > here. > > Well, the sys_sync() that caused your original problem did exactly > that. It's the reason you get deadlocks, right? The sys_sync is unnecessary in the first case. There shouldn't be anything in the suspend path that's going to require userspace access to a device after that device has been suspended. > I agree that in general the suspend process should not have to wait for > a userspace callback to complete. Indeed, there's no particular > reason that anything running during STR should have to wait for > something in userspace to complete. Given that fact, I don't see > anything wrong with freezing userspace when doing STR. There's nothing wrong with it as such, it's just that our implementation appears to suck in a myriad of small ways that keep cropping up and biting people. Even without the sys_sync(), freezing processes results in the suspend failing because syslog is stuck in D state and won't go into the refrigerator. -- Matthew Garrett | mjg59@srcf.ucam.org