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    Subject[PATCH -rt 3/5] asm/local.h cmpxchg
    From: Christoph Lameter <clameter@sgi.com>

    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    ---
    include/asm-generic/local.h | 25 +++++++++++++++++++++++--
    include/asm-i386/local.h | 13 +++++++++++++
    include/asm-x86_64/local.h | 16 ++++++++++++++++
    3 files changed, 52 insertions(+), 2 deletions(-)

    Index: linux-2.6.22-rc6-mm1/include/asm-generic/local.h
    ===================================================================
    --- linux-2.6.22-rc6-mm1.orig/include/asm-generic/local.h 2007-07-12 19:44:18.000000000 -0700
    +++ linux-2.6.22-rc6-mm1/include/asm-generic/local.h 2007-07-12 19:44:57.000000000 -0700
    @@ -46,13 +46,34 @@ typedef struct
    #define local_add_unless(l, a, u) atomic_long_add_unless((&(l)->a), (a), (u))
    #define local_inc_not_zero(l) atomic_long_inc_not_zero(&(l)->a)

    -/* Non-atomic variants, ie. preemption disabled and won't be touched
    - * in interrupt, etc. Some archs can optimize this case well. */
    +/*
    + * Establish a state necessary for __local_xx functions to work.
    + */
    +#define __local_begin(flags) local_irq_disable(flags)
    +
    +static inline void __local_end(unsigned long flags)
    +{
    + local_irq_restore(flags);
    +}
    +
    +/*
    + * Non-atomic variants, ie. within local_begin() / local_end() or
    + * preempt_disable / enable() and won't be touched in interrupt, etc.
    + * Some archs can optimize this case well.
    + */
    #define __local_inc(l) local_set((l), local_read(l) + 1)
    #define __local_dec(l) local_set((l), local_read(l) - 1)
    #define __local_add(i,l) local_set((l), local_read(l) + (i))
    #define __local_sub(i,l) local_set((l), local_read(l) - (i))

    +#define __local_cmpxchg((v), (o), (n)) (*(v) = (n), (o))
    +#define __local_xchg((v), (n)) \
    +({ \
    + __typeof(v) x = *(v); \
    + *(v) = (n); \
    + x; \
    +)}
    +
    /* Use these for per-cpu local_t variables: on some archs they are
    * much more efficient than these naive implementations. Note they take
    * a variable (eg. mystruct.foo), not an address.
    Index: linux-2.6.22-rc6-mm1/include/asm-x86_64/local.h
    ===================================================================
    --- linux-2.6.22-rc6-mm1.orig/include/asm-x86_64/local.h 2007-07-12 19:44:18.000000000 -0700
    +++ linux-2.6.22-rc6-mm1/include/asm-x86_64/local.h 2007-07-12 19:44:57.000000000 -0700
    @@ -9,6 +9,7 @@ typedef struct
    atomic_long_t a;
    } local_t;

    +
    #define LOCAL_INIT(i) { ATOMIC_LONG_INIT(i) }

    #define local_read(l) atomic_long_read(&(l)->a)
    @@ -181,11 +182,26 @@ static __inline__ long local_sub_return(

    /* On x86-64 these are better than the atomic variants on SMP kernels
    because they dont use a lock prefix. */
    +
    +#define __local_begin(__flags) \
    +{ \
    + (__flags) = 0; \
    + preempt_disable(); \
    +}
    +
    +static inline void __local_end(unsigned long flags) {
    + preempt_enable();
    +}
    +
    #define __local_inc(l) local_inc(l)
    #define __local_dec(l) local_dec(l)
    #define __local_add(i,l) local_add((i),(l))
    #define __local_sub(i,l) local_sub((i),(l))

    +#define __local_cmpxchg cmpxchg_local
    +#define __local_xchg xchg
    +
    +
    /* Use these for per-cpu local_t variables: on some archs they are
    * much more efficient than these naive implementations. Note they take
    * a variable, not an address.
    Index: linux-2.6.22-rc6-mm1/include/asm-i386/local.h
    ===================================================================
    --- linux-2.6.22-rc6-mm1.orig/include/asm-i386/local.h 2007-07-12 19:53:00.000000000 -0700
    +++ linux-2.6.22-rc6-mm1/include/asm-i386/local.h 2007-07-12 19:55:22.000000000 -0700
    @@ -194,12 +194,25 @@ static __inline__ long local_sub_return(
    })
    #define local_inc_not_zero(l) local_add_unless((l), 1, 0)

    +#define __local_begin(__flags) \
    +{ \
    + (__flags) = 0; \
    + preempt_disable(); \
    +}
    +
    +static inline void __local_end(unsigned long flags) {
    + preempt_enable();
    +}
    +
    /* On x86, these are no better than the atomic variants. */
    #define __local_inc(l) local_inc(l)
    #define __local_dec(l) local_dec(l)
    #define __local_add(i,l) local_add((i),(l))
    #define __local_sub(i,l) local_sub((i),(l))

    +#define __local_cmpxchg cmpxchg_local
    +#define __local_xchg xchg
    +
    /* Use these for per-cpu local_t variables: on some archs they are
    * much more efficient than these naive implementations. Note they take
    * a variable, not an address.
    --

    -
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