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

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Message-ID: <1bb3ff1c-d89f-8b2b-b898-bb60f77462c4@amd.com>
Date:   Wed, 10 Aug 2022 11:04:13 +0200
From:   Christian König <christian.koenig@....com>
To:     Daniel Vetter <daniel@...ll.ch>
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>,
        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 10.08.22 um 10:33 schrieb Daniel Vetter:
> On Wed, 10 Aug 2022 at 08:52, Christian König <christian.koenig@....com> wrote:
>> 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.
> Hm quickly check and I didn't spot it? There's a few patches from
> Dmitry in the last few pulls, and some more stuff pending, but not
> these two afaics?

Mhm, there is some potential that I wanted to push it but got distracted 
by the re-occurring drm-tip build breakages.

Anyway what I wanted to say is that this stuff should probably go to 
drm-misc-fixes with a CC: stable tag :)

Christian.

> -Daniel
>
>> 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;
>>>>>              }
>>>>>      }
>