Re: [Intel-gfx] [PATCH] drm/i915/guc: Use correct context lock when callig clr_context_registered

[Jani Nikula <jani.nikula@linux.intel.com>]

On Fri, 10 Dec 2021, Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> wrote:
> On 09/12/2021 19:14, Daniele Ceraolo Spurio wrote:
>> 
>> 
>> On 12/9/2021 10:48 AM, Matthew Brost wrote:
>>> s/ce/cn/ when grabbing guc_state.lock before calling
>>> clr_context_registered.
>>>
>>> Fixes: 0f7976506de61 ("drm/i915/guc: Rework and simplify locking")
>>> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
>>> Cc: <stable@vger.kernel.org>
>
> I think Cc: stable is not needed here:
>
> $ git tag --contains 0f7976506de61
> drm-intel-fixes-2021-11-18
> drm-intel-gt-next-2021-10-08
> drm-intel-gt-next-2021-10-21
> drm-intel-gt-next-2021-11-22
> drm-intel-next-2021-10-15
> drm-intel-next-fixes-2021-11-09
> v5.16-rc1
> v5.16-rc2
> v5.16-rc3
> v5.16-rc4

'dim fixes 0f7976506de61' concurs.

BR,
Jani.






>
> So still can hit 5.16 via fixes. Rodrigo, did I get this right and you 
> will be able to pick it up next week or so?
>
>> Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
>> 
>> I'm assuming we didn't see any splat from the lockdep assert in 
>> clr_context_registered in our CI runs because we never hit this case as 
>> it requires 64k+ contexts. Maybe we can add a selftest to purposely 
>> exercise this path? Not a blocker for merging this fix.
>
> Was the bug found by inspection or reported?
>
> Given the buggy function is called steal_guc_id, so if the implication 
> is there is no testing for guc id stealing, then it indeed please add 
> some coverage ASAP.
>
> Regards,
>
> Tvrtko
>
>> 
>> Daniele
>> 
>>> ---
>>>   drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c | 4 ++--
>>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c 
>>> b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
>>> index 1f9d4fde421f..9b7b4f4e0d91 100644
>>> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
>>> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
>>> @@ -1937,9 +1937,9 @@ static int steal_guc_id(struct intel_guc *guc, 
>>> struct intel_context *ce)
>>>           list_del_init(&cn->guc_id.link);
>>>           ce->guc_id = cn->guc_id;
>>> -        spin_lock(&ce->guc_state.lock);
>>> +        spin_lock(&cn->guc_state.lock);
>>>           clr_context_registered(cn);
>>> -        spin_unlock(&ce->guc_state.lock);
>>> +        spin_unlock(&cn->guc_state.lock);
>>>           set_context_guc_id_invalid(cn);
>> 

-- 
Jani Nikula, Intel Open Source Graphics Center