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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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