[Intel-gfx] [PATCH 02/12] drm/i915/gt: Cancel the flush worker more thoroughly

[Chris Wilson]

Quoting Mika Kuoppala (2020-05-25 14:51:18)
> Chris Wilson <chris at chris-wilson.co.uk> writes:
> 
> > Since the worker may rearm, we currently are only guaranteed to flush
> > the work if we cancel the timer. If the work was running at the time we
> > try and cancel it, we will wait for it to complete, but it may leave
> > items in the pool and requeue the work. If we rearrange the immediate
> > discard of the pool then cancel the work, we know that the work cannot
> > rearm and so our flush will be final.
> >
> > <0> [314.146044] i915_mod-1321    2.... 299799443us : intel_gt_fini_buffer_pool: intel_gt_fini_buffer_pool:227 GEM_BUG_ON(!list_empty(&pool->cache_list[n]))
> >
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > ---
> >  drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c b/drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c
> > index 1495054a4305..418ae184cecf 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c
> > @@ -212,8 +212,9 @@ void intel_gt_flush_buffer_pool(struct intel_gt *gt)
> >  {
> >       struct intel_gt_buffer_pool *pool = &gt->buffer_pool;
> >  
> > -     if (cancel_delayed_work_sync(&pool->work))
> > +     do {
> >               pool_free_imm(pool);
> > +     } while (cancel_delayed_work_sync(&pool->work));
> 
> Yeah changing of order makes sense. If you want
> a guarantee that the finit goes as you expect, you
> could add two cancel_delayed_work_sync and assert
> that the final one return false.

We have an assert that the lists are empty after this function returns.
That's enough to keep me [un]happy :)
-Chris