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