Re: [PATCH] drm/ttm: fix missing NULL check in ttm_device_swapout

[Felix Kuehling <felix.kuehling@amd.com>]

[+amd-gfx]


On 2022-06-03 15:37, Felix Kuehling wrote:
>
> On 2022-06-03 06:46, Christian König wrote:
>> Resources about to be destructed are not tied to BOs any more.
> I've been seeing a backtrace in that area with a patch series I'm 
> working on, but didn't have enough time to track it down yet. I'll try 
> if this patch fixes it.

The patch doesn't apply on amd-staging-drm-next. I made the following 
change instead, which fixes my problem (and I do see the pr_err being 
triggered):

--- a/drivers/gpu/drm/ttm/ttm_device.c
+++ b/drivers/gpu/drm/ttm/ttm_device.c
@@ -157,6 +157,10 @@ int ttm_device_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
                         list_for_each_entry(bo, &man->lru[j], lru) {
                                 uint32_t num_pages = PFN_UP(bo->base.size);
  
+                               if (!bo->resource) {
+                                       pr_err("### bo->resource is NULL\n");
+                                       continue;
+                               }
                                 ret = ttm_bo_swapout(bo, ctx, gfp_flags);
                                 /* ttm_bo_swapout has dropped the lru_lock */
                                 if (!ret)

>
> Regards,
>   Felix
>
>
>>
>> Signed-off-by: Christian König <christian.koenig@amd.com>
>> ---
>>   drivers/gpu/drm/ttm/ttm_device.c | 6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/ttm/ttm_device.c 
>> b/drivers/gpu/drm/ttm/ttm_device.c
>> index a0562ab386f5..e7147e304637 100644
>> --- a/drivers/gpu/drm/ttm/ttm_device.c
>> +++ b/drivers/gpu/drm/ttm/ttm_device.c
>> @@ -156,8 +156,12 @@ int ttm_device_swapout(struct ttm_device *bdev, 
>> struct ttm_operation_ctx *ctx,
>>             ttm_resource_manager_for_each_res(man, &cursor, res) {
>>               struct ttm_buffer_object *bo = res->bo;
>> -            uint32_t num_pages = PFN_UP(bo->base.size);
>> +            uint32_t num_pages;
>>   +            if (!bo)
>> +                continue;
>> +
>> +            num_pages = PFN_UP(bo->base.size);
>>               ret = ttm_bo_swapout(bo, ctx, gfp_flags);
>>               /* ttm_bo_swapout has dropped the lru_lock */
>>               if (!ret)