Re: [PATCH v2 4/4] drm/qxl: use qxl pin function

Christian König
2020-09-29T12:01:53Z

Am 29.09.20 um 12:53 schrieb Daniel Vetter:
> On Tue, Sep 29, 2020 at 11:51:15AM +0200, Gerd Hoffmann wrote:
>> Otherwise ttm throws a WARN because we try to pin without a reservation.
>>
>> Fixes: 9d36d4320462 ("drm/qxl: switch over to the new pin interface")
>> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
>> ---
>> drivers/gpu/drm/qxl/qxl_object.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/qxl/qxl_object.c b/drivers/gpu/drm/qxl/qxl_object.c
>> index d3635e3e3267..eb45267d51db 100644
>> --- a/drivers/gpu/drm/qxl/qxl_object.c
>> +++ b/drivers/gpu/drm/qxl/qxl_object.c
>> @@ -145,7 +145,7 @@ int qxl_bo_create(struct qxl_device *qdev,
>> return r;
>> }
>> if (pinned)
>> - ttm_bo_pin(&bo->tbo);
>> + qxl_bo_pin(bo);
> I think this is now after ttm_bo_init, and at that point the object is
> visible to lru users and everything. So I do think you need to grab locks
> here instead of just incrementing the pin count alone.
>
> It's also I think a bit racy, since ttm_bo_init drops the lock, so someone
> might have snuck in and evicted the object already.
>
> I think what you need is to call ttm_bo_init_reserved, then ttm_bo_pin,
> then ttm_bo_unreserve, all explicitly.

Ah, yes Daniel is right. I thought I've fixed that up, but looks like I
only did that for VMWGFX.

Sorry for the noise, fix to correctly address this is underway.

Regards,
Christian.

> -Daniel
>
>> *bo_ptr = bo;
>> return 0;
>> }
>> --
>> 2.27.0
>>