On Fri, May 15, 2015 at 12:09:00PM +0100, Tvrtko Ursulin wrote: > > Hi, > > On 05/15/2015 11:42 AM, Chris Wilson wrote: > >Mika encountered one pathological scenario under X where acquiring all > >the mm locks (required to insert a mmu notifier) was very slow, so slow > >that by the time we tried to lock the struct_mutex with the usual call > >to i915_mutex_lock_interruptible(), X's signal timer had fired causing > >us to restart the ioctl (and so looped indefinitely). > > Indefinite loop? Are you saying userptr creation endlessly fails to manages > to finish in 10ms (or is it even 100ms, forgot what timer Xorg setups up)? > The __mmu_notifier_register call? > > >While I suspect this is the result of another bug (something leaking mm > >perhaps?) we can forgo the error checking and interuptible nature of the > >lock here so we only have to pay the expense once and get on with it. > >This does expose the userptr creation routine to a driver livelock > >though by not being interruptible. > > How is this acceptable then if it can live-lock? How does that happen? If the i915 driver somehow dies it's a lot nicer for the user to be able to hit ^C and get out of trouble again and debug further than make anything touching i915 be stuck forever. But I think this is a justified exception. Queued for -next, thanks for the patch. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
