linux-kernel - Re: [PATCH v5 3/4] drm/vc4: Check for the binner bo before handling OOM interrupt

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Date:   Tue, 23 Apr 2019 10:30:09 +0200
From:   Paul Kocialkowski <paul.kocialkowski@...tlin.com>
To:     Eric Anholt <eric@...olt.net>, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Eben Upton <eben@...pberrypi.org>
Subject: Re: [PATCH v5 3/4] drm/vc4: Check for the binner bo before handling
 OOM interrupt

Hi,

On Mon, 2019-04-15 at 13:48 -0700, Eric Anholt wrote:
> Paul Kocialkowski <paul.kocialkowski@...tlin.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.
> > 
> > Signed-off-by: Paul Kocialkowski <paul.kocialkowski@...tlin.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;
> >  
> > +	if (!bo)
> > +		return;
> > +
> >  	bin_bo_slot = vc4_v3d_get_bin_slot(vc4);
> >  	if (bin_bo_slot < 0) {
> >  		DRM_ERROR("Couldn't allocate binner overflow mem\n");
> > -- 
> > 2.21.0
> 
> I don't think this is going to be race-free.  You're checking outside of
> a lock, then proceeding to use it even if (in patch 4) the bin BO was in
> the process of being freed during the file close path.  Can we put all
> of the overflow process here under the same lock as freeing?

Definitely, sorry I missed that.

Cheers,

Paul

-- 
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com