Re: [PATCH 09/11] drm/ttm: convert EDEADLK into EAGAIN

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Am 15.05.19 um 10:40 schrieb Daniel Vetter:
> On Tue, May 14, 2019 at 02:31:25PM +0200, Christian König wrote:
>> Let userspace try again if we really run into a deadlock during eviction.
>>
>> This has a low chance of live locking, but with guaranteed forward process.
>>
>> Signed-off-by: Christian König <christian.koenig@amd.com>
>> ---
>>   drivers/gpu/drm/ttm/ttm_bo.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
>> index a301c876ae31..ce85cd8b4970 100644
>> --- a/drivers/gpu/drm/ttm/ttm_bo.c
>> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
>> @@ -877,6 +877,8 @@ static int ttm_mem_evict_first(struct ttm_bo_device *bdev,
>>   					    acquire_ctx);
>>   		if (ret) {
>>   			ttm_bo_put(first_bo);
>> +			if (ret == -EDEADLK)
> Is this the ww_mutex EDEADLK or something else? If the former then letting
> that escape unhandling into userspace sounds like a kernel bug ...

Yeah, the problem surfaced because of patch #4. Previously TTM would 
have just ignored all errors and continued to try different placements 
and only return -ENOMEM when we ran out of a possible placements.

I probably need to either fix patch #4 or reorder the patches.

Thanks for the note,
Christian.

> -Daniel
>
>> +				ret = -EAGAIN;
>>   			return ret;
>>   		}
>>   		spin_lock(&glob->lru_lock);
>> -- 
>> 2.17.1
>>
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