Re: [PATCH v7 1/2] drm/gem: Properly annotate WW context on drm_gem_lock_reservations() error

[Daniel Vetter]

On Thu, Jun 30, 2022 at 11:04:04PM +0300, Dmitry Osipenko wrote:
> 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@xxxxxxxxxxxxxxx
> Fixes: 7edc3e3b975b5 ("drm: Add helpers for locking an array of BO reservations.")
> Reviewed-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>

I merged this one to drm-misc-next-fixes. The other one looks like there's
still opens pending, pls resubmit appropriately (and maybe with some
analysis in the commit message of how exactly this impacts other drivers).
-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;
>  		}
>  	}
> -- 
> 2.36.1
> 

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