Re: [PATCH 1/3] drm/ttm: fix ttm_bo_bulk_move_helper

["Christian König" <ckoenig.leichtzumerken-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Am 31.08.2018 um 17:15 schrieb Michel Dänzer:
> On 2018-08-31 3:10 p.m., Christian König wrote:
>> Staring at the function for six hours, just to essentially move one line
>> of code.
> That sucks, but the commit log should describe what the problem was and
> how this patch solves it.
>
>
>> Signed-off-by: Christian König <christian.koenig@amd.com>
>> ---
>>   drivers/gpu/drm/ttm/ttm_bo.c | 13 ++++++++-----
>>   1 file changed, 8 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
>> index 35d53d81f486..138c98902033 100644
>> --- a/drivers/gpu/drm/ttm/ttm_bo.c
>> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
>> @@ -250,15 +250,18 @@ EXPORT_SYMBOL(ttm_bo_move_to_lru_tail);
>>   static void ttm_bo_bulk_move_helper(struct ttm_lru_bulk_move_pos *pos,
>>   				    struct list_head *lru, bool is_swap)
>>   {
>> +	struct list_head *list;
>>   	LIST_HEAD(entries);
>>   	LIST_HEAD(before);
>> -	struct list_head *list1, *list2;
>>   
>> -	list1 = is_swap ? &pos->last->swap : &pos->last->lru;
>> -	list2 = is_swap ? pos->first->swap.prev : pos->first->lru.prev;
>> +	reservation_object_assert_held(pos->last->resv);
>> +	list = is_swap ? &pos->last->swap : &pos->last->lru;
>> +	list_cut_position(&entries, lru, list);
>> +
>> +	reservation_object_assert_held(pos->first->resv);
>> +	list = is_swap ? pos->first->swap.prev : pos->first->lru.prev;
>> +	list_cut_position(&before, &entries, list);
> So the problem was that the first list_cut_position call could result in
> list2 pointing to la-la-land? Good catch!

Yes, exactly. Thought that would be obvious, but going to add that to 
the commit log.

Can I get a tested-by? You where much better at reproducing that than I'm.

Christian.
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