From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: Async suspend-resume patch w/ completions (was: Re: Async suspend-resume patch w/ rwsems) Date: Sat, 12 Dec 2009 18:35:40 +0100 Message-ID: <200912121835.40663.rjw@sisk.pl> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" 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: ACPI Devel Maling List , Linus Torvalds , LKML , pm list List-Id: linux-pm@vger.kernel.org On Saturday 12 December 2009, Alan Stern wrote: > On Sat, 12 Dec 2009, Rafael J. Wysocki wrote: > > > Below is a patch I've just tested, but there's a lockdep problem in it I don't > > know how to solve. Namely, lockdep is apparently unhappy with us not releasing > > the lock taken in device_suspend() and it complains we take it twice in a row > > (which we do, but for another device). I need to use down_read_non_owner() > > to make it shut up and then I also need to use up_read_non_owner() in > > __device_suspend(), although there's the comment in include/linux/rwsem.h > > saying exatly this about that: > > > > /* > > * Take/release a lock when not the owner will release it. > > * > > * [ This API should be avoided as much as possible - the > > * proper abstraction for this case is completions. ] > > */ > > > > (I'd like to know your opinion about that). Yet, that's not all, because next > > it complains during resume that __device_resume() releases a lock it didn't > > acquire, which it clearly does, but that is intentional. Unfortunately, > > there's no up_write_non_owner() ... > > Hah! I knew it! > > How come lockdep didn't complain earlier? What's different about this > patch? Only the nesting annotations? Why should adding annotations > make lockdep less happy? I'm not sure. Perhaps I made a mistake during the previous tests. Rafael