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SubjectRe: [PATCH 1/5] locking: Introduce range reader/writer lock
On Mon, Mar 06, 2017 at 09:03:26PM -0800, Davidlohr Bueso wrote:
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index 88e01e08e279..e4d9eadd2c47 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -154,7 +154,6 @@ config DRM_RADEON
> select HWMON
> select BACKLIGHT_CLASS_DEVICE
> select BACKLIGHT_LCD_SUPPORT
> - select INTERVAL_TREE
> help
> Choose this option if you have an ATI Radeon graphics card. There
> are both PCI and AGP versions. You don't need to choose this to
> @@ -174,7 +173,6 @@ config DRM_AMDGPU
> select HWMON
> select BACKLIGHT_CLASS_DEVICE
> select BACKLIGHT_LCD_SUPPORT
> - select INTERVAL_TREE
> help
> Choose this option if you have a recent AMD Radeon graphics card.
>
> diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig
> index 183f5dc1c3f2..8a9154550f46 100644
> --- a/drivers/gpu/drm/i915/Kconfig
> +++ b/drivers/gpu/drm/i915/Kconfig
> @@ -3,7 +3,6 @@ config DRM_I915
> depends on DRM
> depends on X86 && PCI
> select INTEL_GTT
> - select INTERVAL_TREE
> # we need shmfs for the swappable backing store, and in particular
> # the shmem_readpage() which depends upon tmpfs
> select SHMEM

I presume this is part of making INTERVAL_TREE unconditional; should be
a separate patch, no?


> +/*
> + * The largest range will span [0,RANGE_RWLOCK_INFINITY].
> + */
> +#define RANGE_RWLOCK_INFINITY (~0UL - 1)

That's a strange limit, what's wrong with ~0UL ?

> +
> +struct range_rwlock {
> + struct interval_tree_node node;
> + struct task_struct *task;
> + /* Number of ranges which are blocking acquisition of the lock */
> + unsigned int blocking_ranges;
> + bool reader;
> +};

Hate the name; our rwlock is a spinlock, therefore this thing suggests
it is too.

Also, no bool in structures.

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