Messages in this thread | | | From | Eric Anholt <> | Subject | Re: [PATCH v4 3/4] drm/vc4: Check for the binner bo before handling OOM interrupt | Date | Thu, 04 Apr 2019 13:09:40 -0700 |
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Paul Kocialkowski <paul.kocialkowski@bootlin.com> writes:
> Hey, > > Le mercredi 03 avril 2019 à 11:58 -0700, Eric Anholt a écrit : >> Paul Kocialkowski <paul.kocialkowski@bootlin.com> writes: >> >> > Since the OOM interrupt directly deals with the binner bo, it doesn't >> > make sense to try and handle it without a binner buffer registered. >> > The interrupt will kick again in due time, so we can safely ignore it >> > without a binner bo allocated. >> > >> > Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com> >> > --- >> > drivers/gpu/drm/vc4/vc4_irq.c | 3 +++ >> > 1 file changed, 3 insertions(+) >> > >> > diff --git a/drivers/gpu/drm/vc4/vc4_irq.c b/drivers/gpu/drm/vc4/vc4_irq.c >> > index ffd0a4388752..723dc86b4511 100644 >> > --- a/drivers/gpu/drm/vc4/vc4_irq.c >> > +++ b/drivers/gpu/drm/vc4/vc4_irq.c >> > @@ -64,6 +64,9 @@ vc4_overflow_mem_work(struct work_struct *work) >> > struct vc4_exec_info *exec; >> > unsigned long irqflags; >> >> Since OOM handling is tricky, could we add a comment to help the next >> person try to understand it: >> >> /* The OOM IRQ is level-triggered, so we'll see one at power-on before >> * any jobs are submitted. The OOM IRQ is masked when this work is >> * scheduled, so we can safely return if there's no binner memory >> * (because no client is currently using 3D). When a bin job is >> * later submitted, its tile memory allocation will end up bringing us >> * back to a non-OOM state so the OOM can be triggered again. >> */ >> >> But, actually, I don't see how the OOM IRQ will ever get re-enabled. > > Okay so I investigated that to try and understand what's going on. > We are definitely writing the OUTOMEM bit to V3D_INTDIS just before > scheduling the workqueue, and never re-enable the IRQ when leaving > early in the workqueue because !vc4->bin_bo. > > It turns out that what saves us here is vc4_irq_postinstall being > called from runtime resume at "the right time". Obviously this is more > than fragile, so we should really be re-enabling the IRQ as soon as we > have the binner bo allocated. > > Since we're now allocating at the first non-dumb bo alloc, I think we > need to make sure that we did in fact get the irq and registered the > allocated BO with the workqueue before submitting the rcl. Or does the > hardware provide any mechanism to take that off our hands somehow?
Maybe just enable the OOM interrupt using INTENA in the bin BO allocation's success case? That feels race-free, since it's a level interrupt and even if we were racing the !bin_bo check in the work, we'd end up re-scheduling the work? [unhandled content-type:application/pgp-signature] | |