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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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