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Message-Id: <4B2BB5830200007800026AC7@vpn.id2.novell.com>
Date: Fri, 18 Dec 2009 16:01:55 +0000
From: "Jan Beulich" <JBeulich@...ell.com>
To: <mingo@...e.hu>, <tglx@...utronix.de>, <hpa@...or.com>
Cc: "Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
"Linus Torvalds" <torvalds@...ux-foundation.org>,
"Nick Piggin" <npiggin@...e.de>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] x86: slightly shorten __ticket_spin_trylock() (v3)
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.
v2: 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.
v3: Keep the return value in %eax (or really, %al).
Signed-off-by: Jan Beulich <jbeulich@...ell.com>
Cc: Nick Piggin <npiggin@...e.de>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
arch/x86/include/asm/paravirt.h | 4 ++--
arch/x86/include/asm/paravirt_types.h | 2 +-
arch/x86/include/asm/spinlock.h | 14 ++++++--------
arch/x86/xen/spinlock.c | 2 +-
4 files changed, 10 insertions(+), 12 deletions(-)
--- linux-2.6.33-rc1/arch/x86/include/asm/paravirt.h 2009-12-18 16:05:40.000000000 +0100
+++ 2.6.33-rc1-x86-spin-trylock-simplify/arch/x86/include/asm/paravirt.h 2009-12-03 09:43:42.000000000 +0100
@@ -753,9 +753,9 @@ static __always_inline void arch_spin_lo
PVOP_VCALL2(pv_lock_ops.spin_lock_flags, lock, flags);
}
-static __always_inline int arch_spin_trylock(struct arch_spinlock *lock)
+static __always_inline u8 arch_spin_trylock(struct arch_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 arch_spin_unlock(struct arch_spinlock *lock)
--- linux-2.6.33-rc1/arch/x86/include/asm/paravirt_types.h 2009-12-18 16:05:40.000000000 +0100
+++ 2.6.33-rc1-x86-spin-trylock-simplify/arch/x86/include/asm/paravirt_types.h 2009-12-03 09:43:50.000000000 +0100
@@ -324,7 +324,7 @@ struct pv_lock_ops {
int (*spin_is_contended)(struct arch_spinlock *lock);
void (*spin_lock)(struct arch_spinlock *lock);
void (*spin_lock_flags)(struct arch_spinlock *lock, unsigned long flags);
- int (*spin_trylock)(struct arch_spinlock *lock);
+ u8 (*spin_trylock)(struct arch_spinlock *lock);
void (*spin_unlock)(struct arch_spinlock *lock);
};
--- linux-2.6.33-rc1/arch/x86/include/asm/spinlock.h 2009-12-18 16:05:40.000000000 +0100
+++ 2.6.33-rc1-x86-spin-trylock-simplify/arch/x86/include/asm/spinlock.h 2009-12-10 15:30:52.000000000 +0100
@@ -77,7 +77,7 @@ static __always_inline void __ticket_spi
: "memory", "cc");
}
-static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)
+static __always_inline u8 __ticket_spin_trylock(arch_spinlock_t *lock)
{
int tmp, new;
@@ -87,8 +87,7 @@ static __always_inline int __ticket_spin
"jne 1f\n\t"
LOCK_PREFIX "cmpxchgw %w1,%2\n\t"
"1:"
- "sete %b1\n\t"
- "movzbl %b1,%0\n\t"
+ "sete %b0\n\t"
: "=&a" (tmp), "=&q" (new), "+m" (lock->slock)
:
: "memory", "cc");
@@ -127,7 +126,7 @@ static __always_inline void __ticket_spi
: "memory", "cc");
}
-static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)
+static __always_inline u8 __ticket_spin_trylock(arch_spinlock_t *lock)
{
int tmp;
int new;
@@ -140,9 +139,8 @@ static __always_inline int __ticket_spin
"jne 1f\n\t"
LOCK_PREFIX "cmpxchgl %1,%2\n\t"
"1:"
- "sete %b1\n\t"
- "movzbl %b1,%0\n\t"
- : "=&a" (tmp), "=&q" (new), "+m" (lock->slock)
+ "sete %b0\n\t"
+ : "=&a" (tmp), "=&r" (new), "+m" (lock->slock)
:
: "memory", "cc");
@@ -190,7 +188,7 @@ static __always_inline void arch_spin_lo
__ticket_spin_lock(lock);
}
-static __always_inline int arch_spin_trylock(arch_spinlock_t *lock)
+static __always_inline u8 arch_spin_trylock(arch_spinlock_t *lock)
{
return __ticket_spin_trylock(lock);
}
--- linux-2.6.33-rc1/arch/x86/xen/spinlock.c 2009-12-18 16:05:40.000000000 +0100
+++ 2.6.33-rc1-x86-spin-trylock-simplify/arch/x86/xen/spinlock.c 2009-12-03 09:44:33.000000000 +0100
@@ -136,7 +136,7 @@ static int xen_spin_is_contended(struct
return xl->spinners != 0;
}
-static int xen_spin_trylock(struct arch_spinlock *lock)
+static u8 xen_spin_trylock(struct arch_spinlock *lock)
{
struct xen_spinlock *xl = (struct xen_spinlock *)lock;
u8 old = 1;
--
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