> -----Original Message----- > From: Daniel Vetter [mailto:daniel.vetter@xxxxxxxx] On Behalf Of Daniel > Vetter > Sent: Wednesday, April 27, 2016 3:09 AM > To: Alex Deucher > Cc: Chris Wilson; Daniel Vetter; DRI Development; Deucher, Alexander; Intel > Graphics Development; Daniel Vetter > Subject: Re: [Intel-gfx] [PATCH 08/35] drm: Protect dev->filelist with its own > mutex > > On Wed, Apr 27, 2016 at 09:06:09AM +0200, Daniel Vetter wrote: > > On Tue, Apr 26, 2016 at 05:45:44PM -0400, Alex Deucher wrote: > > > On Tue, Apr 26, 2016 at 4:52 PM, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > wrote: > > > > On Tue, Apr 26, 2016 at 07:29:41PM +0200, Daniel Vetter wrote: > > > >> amdgpu gained dev->struct_mutex usage, and that's because it's > walking > > > >> the dev->filelist list. Protect that list with it's own lock to take > > > >> one more step towards getting rid of struct_mutex usage in drivers > > > >> once and for all. > > > >> > > > >> While doing the conversion I noticed that 2 debugfs files in i915 > > > >> completely lacked appropriate locking. Fix that up too. > > > >> > > > >> v2: don't forget to switch to > drm_gem_object_unreference_unlocked. > > > >> > > > >> Cc: Alex Deucher <alexander.deucher@xxxxxxx> > > > >> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx> > > > > > > > > Just wondering if this worth converting over. Opening/closing isn't > > > > going to be high contention, I hope, though we can certainly write > > > > stress cases for it! The goal for drivers to stop using the struct_mutex > > > > as their BKL, which doesn't preclude keeping the struct_mutex around > for > > > > where it makes sense to have a single mutex rather than a multitude. > > > > > > > > I have some misgivings over this, but only because I think its overkill. > > > > Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > > > > > > I agree with Chris' sentiments. > > > > It's not to have more speed or less contention, but just to have fewer > > things to worry about when reviewing locking. Hence orthogonal locks for > > independent parts. > > > > My goal is that in the end dev->struct_mutex is only used by some existing > > drivers for their internals, plus all the legacy core stuff. And never > > even used by modern drivers. New locks are pretty cheap, and not > dragging > > in the entire legacy horror show has benefits. > > > > When/once I tackle the one thing left (master locking) I might move the > > master handling under this lock too (since it's closely related to open > > files). Not sure yet. > > Oh and the main reason I did it here: Much easier to review using git grep > struct_mutex than auditing codepaths. With this drivers have no reason to > ever grab struct_mutex (not even for debugfs or similar), since the last > remaining bit (master control) really shouldn't be a concern for drivers > ever. > > That also makes reviewing new drivers simpler: Contains struct_mutex? > Reject it! I'm convinced! Thanks for cleaning this up. Alex > > Cheers, Daniel > -- > Daniel Vetter > Software Engineer, Intel Corporation > http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
