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

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Message-ID: <a42237c9-6304-4b06-cede-2175c7e7b87d@amd.com>
Date:   Tue, 5 Jul 2022 13:33:51 +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>, 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>
Cc:     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 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>

> ---
>   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;
>   		}
>   	}