Messages in this thread | | | Subject | Re: [PATCH v4 4/4] drm/vc4: Allocate binner bo when starting to use the V3D | From | Paul Kocialkowski <> | Date | Thu, 04 Apr 2019 14:38:38 +0200 |
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Hi,
Le mercredi 03 avril 2019 à 11:53 -0700, Eric Anholt a écrit : > Paul Kocialkowski <paul.kocialkowski@bootlin.com> writes: > > > The binner bo is not required until the V3D is in use, so avoid > > allocating it at probe and do it on the first non-dumb BO allocation. > > Keep track of which clients are using the V3D and liberate the buffer > > when there is none left. > > > > We also want to keep it alive during runtime suspend/resume to avoid > > failing to allocate it at resume. This happens when the CMA pool is > > full at that point and results in a hard crash. > > > > Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com> > > --- > > drivers/gpu/drm/vc4/vc4_bo.c | 32 ++++++++++++++++++++++++++++++++ > > drivers/gpu/drm/vc4/vc4_drv.c | 9 +++++++++ > > drivers/gpu/drm/vc4/vc4_drv.h | 4 ++++ > > drivers/gpu/drm/vc4/vc4_v3d.c | 13 ------------- > > 4 files changed, 45 insertions(+), 13 deletions(-) > > > > diff --git a/drivers/gpu/drm/vc4/vc4_bo.c b/drivers/gpu/drm/vc4/vc4_bo.c > > index 88ebd681d7eb..b941f09b9378 100644 > > --- a/drivers/gpu/drm/vc4/vc4_bo.c > > +++ b/drivers/gpu/drm/vc4/vc4_bo.c > > @@ -799,6 +799,30 @@ vc4_prime_import_sg_table(struct drm_device *dev, > > return obj; > > } > > > > +static int vc4_prepare_bin_bo(struct drm_device *dev, > > + struct drm_file *file_priv) > > +{ > > + struct vc4_file *vc4file = file_priv->driver_priv; > > + struct vc4_dev *vc4 = to_vc4_dev(dev); > > + int ret; > > + > > + if (!vc4->v3d) > > + return -ENODEV; > > + > > + if (!vc4file->needs_bin_bo) { > > + atomic_inc(&vc4->bin_bo_usecnt); > > + vc4file->needs_bin_bo = true; > > + } > > + > > + if (!vc4->bin_bo) { > > + ret = vc4_v3d_allocate_bin_bo(vc4); > > + if (ret) > > + return ret; > > + } > > + > > This atomic usage looks really racy. For example, multiple clients > could call allocate at the same time and leak one. Or this timeline: > > us them > dec count to 0 > inc count > check bin_bo > free bin_bo
Oh, you're definitely right. Sorry I missed that.
> vc4_v3d_allocate_bin_bo should probably be a vc4_v3d_bin_bo_get() > returning a kref on the BO, called under a lock protecting both one > file_priv being dereferenced by multiple threads in the kernel at the > same time (so file_priv doesn't try to double-get its ref) and multiple > file_privs trying to get the bin_bo at once.
Sounds good, I'll look into it and spin up a new revision soon.
Cheers,
Paul
-- Paul Kocialkowski, Bootlin Embedded Linux and kernel engineering https://bootlin.com
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