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    Subject[PATCH] x86: slightly shorten __ticket_spin_trylock() (v2)
    Since the callers generally expect a boolean value, there's no need to
    zero-extend the outcome of the comparison. It just requires that all
    of x86' trylock implementations have their return type changed
    accordingly.

    Don't use bool for the return type though - this is being frowned on
    and presently doesn't work with the pv-ops patching macros.

    Signed-off-by: Jan Beulich <jbeulich@novell.com>
    Cc: Nick Piggin <npiggin@suse.de>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>

    ---
    arch/x86/include/asm/paravirt.h | 4 ++--
    arch/x86/include/asm/paravirt_types.h | 2 +-
    arch/x86/include/asm/spinlock.h | 12 +++++-------
    arch/x86/xen/spinlock.c | 2 +-
    4 files changed, 9 insertions(+), 11 deletions(-)

    --- linux-2.6.32-rc8/arch/x86/include/asm/paravirt.h 2009-11-20 14:10:50.000000000 +0100
    +++ 2.6.32-rc8-x86-spin-trylock-simplify/arch/x86/include/asm/paravirt.h 2009-12-03 10:24:51.000000000 +0100
    @@ -753,9 +753,9 @@ static __always_inline void __raw_spin_l
    PVOP_VCALL2(pv_lock_ops.spin_lock_flags, lock, flags);
    }

    -static __always_inline int __raw_spin_trylock(struct raw_spinlock *lock)
    +static __always_inline u8 __raw_spin_trylock(struct raw_spinlock *lock)
    {
    - return PVOP_CALL1(int, pv_lock_ops.spin_trylock, lock);
    + return PVOP_CALL1(u8, pv_lock_ops.spin_trylock, lock);
    }

    static __always_inline void __raw_spin_unlock(struct raw_spinlock *lock)
    --- linux-2.6.32-rc8/arch/x86/include/asm/paravirt_types.h 2009-11-20 14:10:50.000000000 +0100
    +++ 2.6.32-rc8-x86-spin-trylock-simplify/arch/x86/include/asm/paravirt_types.h 2009-12-03 10:24:58.000000000 +0100
    @@ -324,7 +324,7 @@ struct pv_lock_ops {
    int (*spin_is_contended)(struct raw_spinlock *lock);
    void (*spin_lock)(struct raw_spinlock *lock);
    void (*spin_lock_flags)(struct raw_spinlock *lock, unsigned long flags);
    - int (*spin_trylock)(struct raw_spinlock *lock);
    + u8 (*spin_trylock)(struct raw_spinlock *lock);
    void (*spin_unlock)(struct raw_spinlock *lock);
    };

    --- linux-2.6.32-rc8/arch/x86/include/asm/spinlock.h 2009-09-10 00:13:59.000000000 +0200
    +++ 2.6.32-rc8-x86-spin-trylock-simplify/arch/x86/include/asm/spinlock.h 2009-12-03 10:26:07.000000000 +0100
    @@ -77,7 +77,7 @@ static __always_inline void __ticket_spi
    : "memory", "cc");
    }

    -static __always_inline int __ticket_spin_trylock(raw_spinlock_t *lock)
    +static __always_inline u8 __ticket_spin_trylock(raw_spinlock_t *lock)
    {
    int tmp, new;

    @@ -88,12 +88,11 @@ static __always_inline int __ticket_spin
    LOCK_PREFIX "cmpxchgw %w1,%2\n\t"
    "1:"
    "sete %b1\n\t"
    - "movzbl %b1,%0\n\t"
    : "=&a" (tmp), "=&q" (new), "+m" (lock->slock)
    :
    : "memory", "cc");

    - return tmp;
    + return new;
    }

    static __always_inline void __ticket_spin_unlock(raw_spinlock_t *lock)
    @@ -127,7 +126,7 @@ static __always_inline void __ticket_spi
    : "memory", "cc");
    }

    -static __always_inline int __ticket_spin_trylock(raw_spinlock_t *lock)
    +static __always_inline u8 __ticket_spin_trylock(raw_spinlock_t *lock)
    {
    int tmp;
    int new;
    @@ -141,12 +140,11 @@ static __always_inline int __ticket_spin
    LOCK_PREFIX "cmpxchgl %1,%2\n\t"
    "1:"
    "sete %b1\n\t"
    - "movzbl %b1,%0\n\t"
    : "=&a" (tmp), "=&q" (new), "+m" (lock->slock)
    :
    : "memory", "cc");

    - return tmp;
    + return new;
    }

    static __always_inline void __ticket_spin_unlock(raw_spinlock_t *lock)
    @@ -190,7 +188,7 @@ static __always_inline void __raw_spin_l
    __ticket_spin_lock(lock);
    }

    -static __always_inline int __raw_spin_trylock(raw_spinlock_t *lock)
    +static __always_inline u8 __raw_spin_trylock(raw_spinlock_t *lock)
    {
    return __ticket_spin_trylock(lock);
    }
    --- linux-2.6.32-rc8/arch/x86/xen/spinlock.c 2009-11-20 14:10:51.000000000 +0100
    +++ 2.6.32-rc8-x86-spin-trylock-simplify/arch/x86/xen/spinlock.c 2009-12-03 10:26:47.000000000 +0100
    @@ -136,7 +136,7 @@ static int xen_spin_is_contended(struct
    return xl->spinners != 0;
    }

    -static int xen_spin_trylock(struct raw_spinlock *lock)
    +static u8 xen_spin_trylock(struct raw_spinlock *lock)
    {
    struct xen_spinlock *xl = (struct xen_spinlock *)lock;
    u8 old = 1;



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