[PATCH] drm/ttm: set bo->resv point to tbo->ttm_resv after individualize_resv

He, Roger Hongbo.He at amd.com
Wed Nov 8 07:11:21 UTC 2017

I guess this because you move the resv changing out of lock of bo->resv.
Because at the beginning ttm_mem_evict_first may __ttm_bo_reserve(bo->resv) success, and then bo->resv has been changed by another thread. That is not matched and at this point bo->ttm_resv also may been freed already.

 And I think it is not easy to put it out of two lock of bo->resv and bo->ttm_resv.

-----Original Message-----
From: dri-devel [mailto:dri-devel-bounces at lists.freedesktop.org] On Behalf Of Michel D?nzer
Sent: Wednesday, November 08, 2017 12:16 AM
To: Christian König <ckoenig.leichtzumerken at gmail.com>
Cc: dri-devel at lists.freedesktop.org; amd-gfx at lists.freedesktop.org
Subject: Re: [PATCH] drm/ttm: set bo->resv point to tbo->ttm_resv after individualize_resv

On 07/11/17 02:44 PM, Christian König wrote:
> Set bo->resv to ttm_resv during BO cleanup. This way freed BOs can be 
> better reaped during eviction.
> Signed-off-by: Roger He <Hongbo.He at amd.com>
> Signed-off-by: Christian König <christian.koenig at amd.com>

KASAN caught some badness while running piglit with this applied, see the attached dmesg excerpts.

At least some of this might be pre-existing bugs being exposed by this change. E.g. I've been chasing another use-after-free, with ttm_bo_delayed_delete trying to reserve a BO which has already been destroyed. Looks like maybe the ddestroy list handling isn't quite watertight yet.

Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer

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