linux-kernel - Re: [PATCH v8 1/2] drm/gem: Properly annotate WW context on drm_gem_lock

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Date:   Tue, 9 Aug 2022 18:44:22 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Christian König <christian.koenig@....com>
Cc:     Dmitry Osipenko <dmitry.osipenko@...labora.com>,
        David Airlie <airlied@...ux.ie>,
        Gerd Hoffmann <kraxel@...hat.com>,
        Gurchetan Singh <gurchetansingh@...omium.org>,
        Chia-I Wu <olvaffe@...il.com>, Daniel Vetter <daniel@...ll.ch>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Emil Velikov <emil.l.velikov@...il.com>,
        Thomas Hellström <thomas_os@...pmail.org>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Dmitry Osipenko <digetx@...il.com>,
        linux-tegra@...r.kernel.org, kernel@...labora.com,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v8 1/2] drm/gem: Properly annotate WW context on
 drm_gem_lock_reservations() error

On Tue, Jul 05, 2022 at 01:33:51PM +0200, Christian König wrote:
> Am 01.07.22 um 11:02 schrieb Dmitry Osipenko:
> > Use ww_acquire_fini() in the error code paths. Otherwise lockdep
> > thinks that lock is held when lock's memory is freed after the
> > drm_gem_lock_reservations() error. The ww_acquire_context needs to be
> > annotated as "released", which fixes the noisy "WARNING: held lock freed!"
> > splat of VirtIO-GPU driver with CONFIG_DEBUG_MUTEXES=y and enabled lockdep.
> > 
> > Cc: stable@...r.kernel.org
> > Fixes: 7edc3e3b975b5 ("drm: Add helpers for locking an array of BO reservations.")
> > Reviewed-by: Thomas Hellström <thomas.hellstrom@...ux.intel.com>
> > Signed-off-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>
> 
> Reviewed-by: Christian König <christian.koenig@....com>

Also added this r-b tag when merging to drm-misc-next-fixes.
-Daniel

> 
> > ---
> >   drivers/gpu/drm/drm_gem.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> > index eb0c2d041f13..86d670c71286 100644
> > --- a/drivers/gpu/drm/drm_gem.c
> > +++ b/drivers/gpu/drm/drm_gem.c
> > @@ -1226,7 +1226,7 @@ drm_gem_lock_reservations(struct drm_gem_object **objs, int count,
> >   		ret = dma_resv_lock_slow_interruptible(obj->resv,
> >   								 acquire_ctx);
> >   		if (ret) {
> > -			ww_acquire_done(acquire_ctx);
> > +			ww_acquire_fini(acquire_ctx);
> >   			return ret;
> >   		}
> >   	}
> > @@ -1251,7 +1251,7 @@ drm_gem_lock_reservations(struct drm_gem_object **objs, int count,
> >   				goto retry;
> >   			}
> > -			ww_acquire_done(acquire_ctx);
> > +			ww_acquire_fini(acquire_ctx);
> >   			return ret;
> >   		}
> >   	}
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch