Quoting Tvrtko Ursulin (2020-07-08 13:18:21)
>
> On 06/07/2020 07:19, Chris Wilson wrote:
> > Currently, if an error is raised we always call the cleanup locally
> > [and skip the main work callback]. However, some future users may need
> > to take a mutex to cleanup and so we cannot immediately execute the
> > cleanup as we may still be in interrupt context.
> >
> > With the execute-immediate flag, for most cases this should result in
> > immediate cleanup of an error.
> >
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/i915_sw_fence_work.c | 25 +++++++++++------------
> > 1 file changed, 12 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_sw_fence_work.c b/drivers/gpu/drm/i915/i915_sw_fence_work.c
> > index a3a81bb8f2c3..29f63ebc24e8 100644
> > --- a/drivers/gpu/drm/i915/i915_sw_fence_work.c
> > +++ b/drivers/gpu/drm/i915/i915_sw_fence_work.c
> > @@ -16,11 +16,14 @@ static void fence_complete(struct dma_fence_work *f)
> > static void fence_work(struct work_struct *work)
> > {
> > struct dma_fence_work *f = container_of(work, typeof(*f), work);
> > - int err;
> >
> > - err = f->ops->work(f);
> > - if (err)
> > - dma_fence_set_error(&f->dma, err);
> > + if (!f->dma.error) {
> > + int err;
> > +
> > + err = f->ops->work(f);
> > + if (err)
> > + dma_fence_set_error(&f->dma, err);
> > + }
> >
> > fence_complete(f);
> > dma_fence_put(&f->dma);
> > @@ -36,15 +39,11 @@ fence_notify(struct i915_sw_fence *fence, enum i915_sw_fence_notify state)
> > if (fence->error)
> > dma_fence_set_error(&f->dma, fence->error);
> >
> > - if (!f->dma.error) {
> > - dma_fence_get(&f->dma);
> > - if (test_bit(DMA_FENCE_WORK_IMM, &f->dma.flags))
> > - fence_work(&f->work);
> > - else
> > - queue_work(system_unbound_wq, &f->work);
> > - } else {
> > - fence_complete(f);
> > - }
> > + dma_fence_get(&f->dma);
> > + if (test_bit(DMA_FENCE_WORK_IMM, &f->dma.flags))
> > + fence_work(&f->work);
> > + else
> > + queue_work(system_unbound_wq, &f->work);
>
> Right the commit wording really confused me since it is obviously still
> deferring stuff to the worker. By "fenced work" I understand you
> actually mean more like "never signal non-immediate work from the notify
> callback" (even in the error case).
Work that had to wait for a fence should always take the worker to avoid
being run in interrupt context (from the fence signal callback), even in
the case of errors [so that the work can take its carefully considered
mutexes]. I anticipate that most errors will be generated before we
starting waiting for fences, and those will remain immediately executed
(when asked to do so by the caller).
-Chris
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