From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Anholt Subject: Re: [PATCH v4 4/4] drm/vc4: Allocate binner bo when starting to use the V3D Date: Wed, 03 Apr 2019 11:53:27 -0700 Message-ID: <87ftqyor88.fsf@anholt.net> References: <20190403154856.9470-1-paul.kocialkowski@bootlin.com> <20190403154856.9470-5-paul.kocialkowski@bootlin.com> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha512; protocol="application/pgp-signature" Return-path: In-Reply-To: <20190403154856.9470-5-paul.kocialkowski@bootlin.com> Sender: linux-kernel-owner@vger.kernel.org To: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Cc: David Airlie , Daniel Vetter , Thomas Petazzoni , Maxime Ripard , Eben Upton , Daniel Stone , Paul Kocialkowski List-Id: dri-devel@lists.freedesktop.org --=-=-= Content-Type: text/plain Content-Transfer-Encoding: quoted-printable Paul Kocialkowski 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 > --- > 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; > } >=20=20 > +static int vc4_prepare_bin_bo(struct drm_device *dev, > + struct drm_file *file_priv) > +{ > + struct vc4_file *vc4file =3D file_priv->driver_priv; > + struct vc4_dev *vc4 =3D 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 =3D true; > + } > + > + if (!vc4->bin_bo) { > + ret =3D 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 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. --=-=-= Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEE/JuuFDWp9/ZkuCBXtdYpNtH8nugFAlylASgACgkQtdYpNtH8 nui6yxAAhNRgTwjZnkulsLdH3fl2EY+wFqNeL7MN6wTSIEB2Tfn5IAjizq+TgARd dqlXdArGiQrXwib4UljTbocOAOAM1MWUiY9RESeqIuQoy1h7OBpxw9c8PEX2PJUw oNuCKCGqxIQqFA8OW3EcTModbs+QaxPrc+m7se3T+1ppGlVL9N+EapT9CEdMlq3J lgFirN/OQJ/dmyVowGgDnwoADKNIWclWHoieTdiBxVOqbDxPdy6sFOfr36regVXp Am0qPllon1KcpcECJKWAk7rrr0BkAENkPj1pOfrGhEaSQrKGBENF0IRQXqyzlbvo 7uQlVPNcL1k+6euvDO1zatbxOfSA6Gu+aDw9sfwL723FoeZT292Sl8QALGgDsrv0 dQmfqTpEbvvdfUvLAbOr0v9iLYQPT1DBup50jOHg4D4bgAkDmec1GUnu+qMDAeLp qhQMf5Wvovb6f6Px5nBlfbbqboETFnsH7RtNzx1v4z7C9ey4p1Jfl8eb+sf++F3i PT6hAa5EhU9XUunYDNcpyKm9nlNxxXPKD2Fiol1PB/aVnZ07pGTcnES2IFnR/JAA 7GI3xy8JTUihxh1v0N7uC4wjbwHvKZuxCrWjfvH4zAelPy6FlFIFZus1bYq0+4Fu yiTAWR2ObpW3BzypUV6kInd1LuFYksRuCm4f4z+YO/HHW05GhbU= =2Y6S -----END PGP SIGNATURE----- --=-=-=--