[Intel-gfx] [PATCH v2] RFC drm/i915: Mark runtime_pm as a special class of lock

[Chris Wilson]

Quoting Chris Wilson (2018-07-12 09:36:33)
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/i915_drv.c         |  5 +++++
>  drivers/gpu/drm/i915/i915_drv.h         |  1 +
>  drivers/gpu/drm/i915/intel_runtime_pm.c | 11 +++++++++++
>  3 files changed, 17 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index 3eba3d1ab5b8..2e6d3259f6d0 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -2603,6 +2603,7 @@ static int intel_runtime_suspend(struct device *kdev)
>         DRM_DEBUG_KMS("Suspending device\n");
>  
>         disable_rpm_wakeref_asserts(dev_priv);
> +       lock_map_acquire(&dev_priv->runtime_pm.lock);
>  
>         /*
>          * We are safe here against re-faults, since the fault handler takes
> @@ -2637,11 +2638,13 @@ static int intel_runtime_suspend(struct device *kdev)
>                 i915_gem_init_swizzling(dev_priv);
>                 i915_gem_restore_fences(dev_priv);
>  
> +               lock_map_release(&dev_priv->runtime_pm.lock);
>                 enable_rpm_wakeref_asserts(dev_priv);
>  
>                 return ret;
>         }
>  
> +       lock_map_release(&dev_priv->runtime_pm.lock);

What happens if we don't release the lock here? I think that's what we
want... While suspended we are not allowed to do any action that would
ordinarily require a wakeref. However that scares me for being both
incredibly broad, and that I think lockdep is process centric so doesn't
track locks in this manner?
-Chris