Re: [PATCH] drm/i915/selftests: Fix build after dma-fence locking rework

[Christian König <christian.koenig@amd.com>]

On 2/23/26 20:20, Matthew Brost wrote:
> On Mon, Feb 23, 2026 at 08:13:34PM +0100, Christian König wrote:
>> On 2/23/26 18:25, Matthew Brost wrote:
>>> The i915_active selftest no longer builds after the dma-fence locking
>>> rework because it directly accessed the fence’s spinlock. The helper
>>> dma_fence_spinlock() must now be used to obtain the spinlock. Update the
>>> selftest to use dma_fence_spinlock() accordingly.
>>>
>>> Fixes: 1f32f310a13c ("dma-buf: inline spinlock for fence protection v5")
>>> Cc: Christian König <christian.koenig@amd.com>
>>> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
>>
>> Reviewed-by: Christian König <christian.koenig@amd.com>
>>
>> Thanks for the patch and sorry for the noise, just one more question below.
>>
>>> ---
>>>  drivers/gpu/drm/i915/selftests/i915_active.c | 4 ++--
>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/selftests/i915_active.c b/drivers/gpu/drm/i915/selftests/i915_active.c
>>> index 52345073b409..9fea2fabeac4 100644
>>> --- a/drivers/gpu/drm/i915/selftests/i915_active.c
>>> +++ b/drivers/gpu/drm/i915/selftests/i915_active.c
>>> @@ -323,9 +323,9 @@ static void active_flush(struct i915_active *ref,
>>>  	if (!fence)
>>>  		return;
>>>  
>>> -	spin_lock_irq(fence->lock);
>>> +	spin_lock_irq(dma_fence_spinlock(fence));
>>
>> Is it guaranteed that this is called from interrupt context? E.g. why is spin_lock_irq() instead of spin_lock_irqsafe() used here?
>>
> 
> Idk, this i915 stuff I’ve long intentionally tried to forget to avoid nightmares.
> 
>> That's basically the reason why I missed this.
>>
> 
> Also, please include the intel-xe list for CI — that will catch issues as well.
> 
> We’re making it a bit further now, but we’re hitting a lockdep splat [1].

^^ that actually looks like a bug in dma_fence_chain_enable_signaling() which was there before the patch set and now just get bubbled up because lockdep can finally check on it.

Just reverting "dma-buf: use inline lock for the dma-fence-chain" should silence that again, but it is clearly not the right fix.

> I can dig into it now; hopefully it’s an easy fix. If not, I may ask for
> a revert. Give me an hour or so to look into it and I’ll report back.
> But again, please include the intel-xe list for CI on risky DRM common
> or dma-buf patches — if the patches apply to drm-tip, CI will run. You
> should have permission to trigger this; I believe all AMD emails do.

I did that on an older version of the patch set but never got a report back. My assumption was that it's working but could be that this actually never ran.

Regards,
Christian.

> 
> Matt  
> 
> [1] https://intel-gfx-ci.01.org/tree/intel-xe/xe-pw-161999v1/bat-ptl-1/igt@xe_compute@compute-square.html
> 
>> Regards,
>> Christian.
>>
>>>  	__list_del_entry(&active->cb.node);
>>> -	spin_unlock_irq(fence->lock); /* serialise with fence->cb_list */
>>> +	spin_unlock_irq(dma_fence_spinlock(fence)); /* serialise with fence->cb_list */
>>>  	atomic_dec(&ref->count);
>>>  
>>>  	GEM_BUG_ON(!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags));
>>