Re: [igt-dev] [Intel-gfx] [PATCH igt 2/2] igt/gem_eio: Drop DRM_MASTER so we can reacquire it in the subtests

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 06/04/2018 09:51, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2018-04-06 09:35:41)
>>
>> On 05/04/2018 19:47, Chris Wilson wrote:
>>> As we reopen the fd for each subtest, and we need a DRM_MASTER, we need
>>> to drop master on the original before we are allowed to claim DRM_MASTER
>>> on the second.
>>>
>>> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
>>> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>> ---
>>>    tests/gem_eio.c | 2 ++
>>>    1 file changed, 2 insertions(+)
>>>
>>> diff --git a/tests/gem_eio.c b/tests/gem_eio.c
>>> index 9599e73d..66d8c18a 100644
>>> --- a/tests/gem_eio.c
>>> +++ b/tests/gem_eio.c
>>> @@ -41,6 +41,7 @@
>>>    #include <drm.h>
>>>    
>>>    #include "igt.h"
>>> +#include "igt_device.h"
>>>    #include "igt_sysfs.h"
>>>    #include "sw_sync.h"
>>>    
>>> @@ -674,6 +675,7 @@ igt_main
>>>    
>>>        igt_fixture {
>>>                fd = drm_open_driver(DRIVER_INTEL);
>>> +             igt_device_drop_master(fd);
>>
>>
>> Is it master by default? I can't spot a place which would set master
>> either in igt/lib/ or in drm.
> 
> First person to open /dev/dri/cardN gets DRM_MASTER.

Weird. And I missed to spot that magic while browsing around.

>> But in any case, should we have gem_reopen_driver attempt to drop master
>> before re-opening? And if it was successful, drop it again after
>> re-opening to end up in the same state?
> 
> Not sure. I can argue the alternative as well, what if we were testing
> authentication and wanted to keep DRM_MASTER and spawn a !MASTER fd.
> My first thought was the same, gem_reopen_fd() should try to ensure the
> new fd has the same caps as the original, but API they be tricky to rule
> out surprises. For me it's easier to say, gem_reopen_fd() follows the
> DRM convention in that the second fd will not be DRM_MASTER unless you
> play the DRM games. Then you can choose what games to play?

Okay, pragmatic response says:

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Apologies for causing breakage.

Regards,

Tvrtko
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