Re: [PATCH v2 1/6] drm/i915/gem: fix bitwise and logical AND mixup

[Matthew Auld <matthew.auld@intel.com>]

On 30/09/2024 14:54, Jani Nikula wrote:
> On Fri, 27 Sep 2024, Jani Nikula <jani.nikula@intel.com> wrote:
>> On Thu, 26 Sep 2024, Rodrigo Vivi <rodrigo.vivi@intel.com> wrote:
>>> On Wed, Sep 18, 2024 at 08:35:43PM +0300, Jani Nikula wrote:
>>>> CONFIG_DRM_I915_USERFAULT_AUTOSUSPEND is an int, defaulting to 250. When
>>>> the wakeref is non-zero, it's either -1 or a dynamically allocated
>>>> pointer, depending on CONFIG_DRM_I915_DEBUG_RUNTIME_PM. It's likely that
>>>> the code works by coincidence with the bitwise AND, but with
>>>> CONFIG_DRM_I915_DEBUG_RUNTIME_PM=y, there's the off chance that the
>>>> condition evaluates to false, and intel_wakeref_auto() doesn't get
>>>> called. Switch to the intended logical AND.
>>>>
>>>> v2: Use != to avoid clang -Wconstant-logical-operand (Nathan)
>>>
>>> oh, this is ugly!
>>>
>>> Wouldn't it be better then to use IS_ENABLED() macro?
>>
>> It's an int config option, not a bool. (Yes, the name is misleading.)
>>
>> IS_ENABLED(CONFIG_DRM_I915_USERFAULT_AUTOSUSPEND) would be the same as
>> CONFIG_DRM_I915_USERFAULT_AUTOSUSPEND == 1.
>>
>> We're actually checking if the int value != 0, so IMO the patch at hand
>> is fine.
> 
> Ping, r-b on this one too?

r-b still holds for v2, fwiw.

> 
> BR,
> Jani.
> 
>>
>> BR,
>> Jani.
>>
>>
>>>
>>>>
>>>> Fixes: ad74457a6b5a ("drm/i915/dgfx: Release mmap on rpm suspend")
>>>> Cc: Matthew Auld <matthew.auld@intel.com>
>>>> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
>>>> Cc: Anshuman Gupta <anshuman.gupta@intel.com>
>>>> Cc: Andi Shyti <andi.shyti@linux.intel.com>
>>>> Cc: Nathan Chancellor <nathan@kernel.org>
>>>> Cc: <stable@vger.kernel.org> # v6.1+
>>>> Reviewed-by: Matthew Auld <matthew.auld@intel.com> # v1
>>>> Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com> # v1
>>>> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>>>> ---
>>>>   drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 2 +-
>>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
>>>> index 5c72462d1f57..b22e2019768f 100644
>>>> --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
>>>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
>>>> @@ -1131,7 +1131,7 @@ static vm_fault_t vm_fault_ttm(struct vm_fault *vmf)
>>>>   		GEM_WARN_ON(!i915_ttm_cpu_maps_iomem(bo->resource));
>>>>   	}
>>>>   
>>>> -	if (wakeref & CONFIG_DRM_I915_USERFAULT_AUTOSUSPEND)
>>>> +	if (wakeref && CONFIG_DRM_I915_USERFAULT_AUTOSUSPEND != 0)
>>>>   		intel_wakeref_auto(&to_i915(obj->base.dev)->runtime_pm.userfault_wakeref,
>>>>   				   msecs_to_jiffies_timeout(CONFIG_DRM_I915_USERFAULT_AUTOSUSPEND));
>>>>   
>>>> -- 
>>>> 2.39.2
>>>>
>