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

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On 30/09/2024 14:54, Jani Nikula wrote:
On Fri, 27 Sep 2024, Jani Nikula <jani.nikula@xxxxxxxxx> wrote:
On Thu, 26 Sep 2024, Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx> 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@xxxxxxxxx>
Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Cc: Anshuman Gupta <anshuman.gupta@xxxxxxxxx>
Cc: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx>
Cc: Nathan Chancellor <nathan@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v6.1+
Reviewed-by: Matthew Auld <matthew.auld@xxxxxxxxx> # v1
Reviewed-by: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx> # v1
Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
---
  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






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