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

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Message-ID: <e760f555-7f2d-dea9-70b2-c0881adc3afc@amd.com>
Date:   Wed, 10 Aug 2022 08:52:18 +0200
From:   Christian König <christian.koenig@....com>
To:     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>,
        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

Am 09.08.22 um 18:44 schrieb Daniel Vetter:
> 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.

IIRC I've already pushed this to drm-misc-fixes with a CC stable tag 
about 2 weeks ago.

Please double check, it probably just hasn't come down the stream again yet.

Christian.

> -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;
>>>    		}
>>>    	}