linux-kernel - Re: [Intel-gfx] [PATCH 3/4] drm/ttm: Don't leak a resource on eviction error

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Date:   Thu, 22 Jun 2023 16:08:32 +0200
From:   Thomas Hellström 
        <thomas.hellstrom@...ux.intel.com>
To:     Andi Shyti <andi.shyti@...ux.intel.com>
Cc:     intel-xe@...ts.freedesktop.org,
        Andrey Grodzovsky <andrey.grodzovsky@....com>,
        Christian König <ckoenig.leichtzumerken@...il.com>,
        intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, Huang Rui <ray.huang@....com>,
        dri-devel@...ts.freedesktop.org,
        Christian König <christian.koenig@....com>
Subject: Re: [Intel-gfx] [PATCH 3/4] drm/ttm: Don't leak a resource on
 eviction error


On 6/22/23 15:55, Andi Shyti wrote:
> Hi Thomas,
>
> On Thu, Jun 22, 2023 at 12:14:11PM +0200, Thomas Hellström wrote:
>> On eviction errors other than -EMULTIHOP we were leaking a resource.
>> Fix.
>>
>> Fixes: 403797925768 ("drm/ttm: Fix multihop assert on eviction.")
>> Cc: Andrey Grodzovsky <andrey.grodzovsky@....com>
>> Cc: Christian König <christian.koenig@....com>
>> Cc: Christian Koenig <christian.koenig@....com>
>> Cc: Huang Rui <ray.huang@....com>
>> Cc: dri-devel@...ts.freedesktop.org
>> Cc: <stable@...r.kernel.org> # v5.15+
>> Signed-off-by: Thomas Hellström <thomas.hellstrom@...ux.intel.com>
>> ---
>>   drivers/gpu/drm/ttm/ttm_bo.c | 16 ++++++++--------
>>   1 file changed, 8 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
>> index 615d30c4262d..89530f2a027f 100644
>> --- a/drivers/gpu/drm/ttm/ttm_bo.c
>> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
>> @@ -462,14 +462,14 @@ static int ttm_bo_evict(struct ttm_buffer_object *bo,
>>   	ret = ttm_bo_handle_move_mem(bo, evict_mem, true, ctx, &hop);
>>   	if (ret == -EMULTIHOP) {
>>   		ret = ttm_bo_bounce_temp_buffer(bo, &evict_mem, ctx, &hop);
>> -		if (ret) {
>> -			if (ret != -ERESTARTSYS && ret != -EINTR)
>> -				pr_err("Buffer eviction failed\n");
>> -			ttm_resource_free(bo, &evict_mem);
>> -			goto out;
>> -		}
>> -		/* try and move to final place now. */
>> -		goto bounce;
>> +		if (!ret)
>> +			/* try and move to final place now. */
>> +			goto bounce;
> As we are at this, can't we replace this with a while()? Goto's
> used instead of a while loop are a fist in the eye...

I'm completely OK with that. this patch already did away with one of 
them. Let's hear Christian's opinion first, though.

Thanks,

Thomas





>
> It looks even better:
>
> 	while (1) {
> 		ret = ttm_bo_handle_move_mem(bo, evict_mem, true, ctx, &hop);
> 		if (!ret)
> 			break;
>
> 		if (ret == -EMULTIHOP)
> 			ret = ttm_bo_bounce_temp_buffer(bo, &evict_mem,
> 							ctx, &hop);
>
> 		/* try again */
> 		if (!ret)
> 			continue;
>
> 		ttm_resource_free(bo, &evict_mem);
> 		if (ret != -ERESTARTSYS && ret != -EINTR)
> 			pr_err("Buffer eviction failed\n");
>
> 		break;
> 	}
>
> Andi
>
>> +	}
>> +	if (ret) {
>> +		ttm_resource_free(bo, &evict_mem);
>> +		if (ret != -ERESTARTSYS && ret != -EINTR)
>> +			pr_err("Buffer eviction failed\n");
>>   	}
>>   out:
>>   	return ret;
>> -- 
>> 2.40.1