From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Subject: Re: [PATCH 3/5] mm, notifier: Catch sleeping/blocking for !blockable Date: Thu, 15 Aug 2019 09:02:49 +0200 Message-ID: <20190815070249.GB7444@phenom.ffwll.local> References: <20190814202027.18735-1-daniel.vetter@ffwll.ch> <20190814202027.18735-4-daniel.vetter@ffwll.ch> <20190815000029.GC11200@ziepe.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20190815000029.GC11200@ziepe.ca> Sender: linux-kernel-owner@vger.kernel.org To: Jason Gunthorpe Cc: Daniel Vetter , LKML , linux-mm@kvack.org, DRI Development , Intel Graphics Development , Andrew Morton , Michal Hocko , David Rientjes , Christian =?iso-8859-1?Q?K=F6nig?= , =?iso-8859-1?B?Suly9G1l?= Glisse , Daniel Vetter List-Id: intel-gfx@lists.freedesktop.org On Wed, Aug 14, 2019 at 09:00:29PM -0300, Jason Gunthorpe wrote: > On Wed, Aug 14, 2019 at 10:20:25PM +0200, Daniel Vetter wrote: > > We need to make sure implementations don't cheat and don't have a > > possible schedule/blocking point deeply burried where review can't > > catch it. > > > > I'm not sure whether this is the best way to make sure all the > > might_sleep() callsites trigger, and it's a bit ugly in the code flow. > > But it gets the job done. > > > > Inspired by an i915 patch series which did exactly that, because the > > rules haven't been entirely clear to us. > > I thought lockdep already was able to detect: > > spin_lock() > might_sleep(); > spin_unlock() > > Am I mistaken? If yes, couldn't this patch just inject a dummy lockdep > spinlock? Hm ... assuming I didn't get lost in the maze I think might_sleep (well ___might_sleep) doesn't do any lockdep checking at all. And we want might_sleep, since that catches a lot more than lockdep. Maybe you mixed it up with the hard/softirq context stuff that lockdep tracks and complains about if you get it wrong? -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch