[Intel-gfx] [PATCH] drm/i915/selftests: Let other struct_mutex users have their gpu time

[Chris Wilson]

Quoting Tvrtko Ursulin (2018-07-03 10:27:47)
> 
> On 03/07/2018 09:30, Chris Wilson wrote:
> > @@ -169,6 +177,8 @@ static int igt_ppgtt_alloc(void *arg)
> >               ppgtt->vm.clear_range(&ppgtt->vm, 0, size);
> >       }
> >   
> > +     schedule_locked(i915);
> > +
> 
> Is it needed in this test? I glanced over and couldn't spot anything 
> struct mutexy in page table only manipulations it does.

struct_mutex is the guard for all drm_mm/i915_address_space, so while we
may not need it exactly in this instance, it is the current mutex to
use. I do have per-vm mutexes in the queue, it's quite scary.

> > @@ -988,14 +1010,14 @@ static int exercise_ppgtt(struct drm_i915_private *dev_priv,
> >       GEM_BUG_ON(offset_in_page(ppgtt->vm.total));
> >       GEM_BUG_ON(ppgtt->vm.closed);
> >   
> > -     err = func(dev_priv, &ppgtt->vm, 0, ppgtt->vm.total, end_time);
> > +     err = func(i915, &ppgtt->vm, 0, ppgtt->vm.total, end_time);
> 
> How about a less hacky solution where func is called unlocked it is 
> responsible to take struct_mutex across the parts which need it?

Convenience. Single threaded tests that didn't want to care about the
details of struct_mutex. And then CI sets itself up in annoying ways!
-Chris