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Subject[tip:core/locking] locking, x86: Slightly shorten __ticket_spin_trylock()
Commit-ID:  133ec7a235160dd44cbd4d82fff65a9983331df9
Gitweb: http://git.kernel.org/tip/133ec7a235160dd44cbd4d82fff65a9983331df9
Author: Jan Beulich <JBeulich@novell.com>
AuthorDate: Fri, 27 Nov 2009 15:09:16 +0000
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Wed, 2 Dec 2009 11:11:11 +0100

locking, x86: Slightly shorten __ticket_spin_trylock()

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 return bool
instead of int.

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>
Cc: H. Peter Anvin <hpa@zytor.com>
LKML-Reference: <4B0FF9AC0200007800022713@vpn.id2.novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
arch/x86/include/asm/paravirt.h | 4 ++--
arch/x86/include/asm/paravirt_types.h | 2 +-
arch/x86/include/asm/spinlock.h | 17 ++++++++---------
arch/x86/xen/spinlock.c | 2 +-
4 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index efb3899..5418dfd 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -753,9 +753,9 @@ static __always_inline void __raw_spin_lock_flags(struct raw_spinlock *lock,
PVOP_VCALL2(pv_lock_ops.spin_lock_flags, lock, flags);
}

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

static __always_inline void __raw_spin_unlock(struct raw_spinlock *lock)
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 9357473..e289f81 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -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);
+ bool (*spin_trylock)(struct raw_spinlock *lock);
void (*spin_unlock)(struct raw_spinlock *lock);
};

diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
index 4e77853..f3db56f 100644
--- a/arch/x86/include/asm/spinlock.h
+++ b/arch/x86/include/asm/spinlock.h
@@ -77,9 +77,10 @@ static __always_inline void __ticket_spin_lock(raw_spinlock_t *lock)
: "memory", "cc");
}

-static __always_inline int __ticket_spin_trylock(raw_spinlock_t *lock)
+static __always_inline bool __ticket_spin_trylock(raw_spinlock_t *lock)
{
- int tmp, new;
+ int tmp;
+ union { int i; bool b; } new;

asm volatile("movzwl %2, %0\n\t"
"cmpb %h0,%b0\n\t"
@@ -88,12 +89,11 @@ static __always_inline int __ticket_spin_trylock(raw_spinlock_t *lock)
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.b;
}

static __always_inline void __ticket_spin_unlock(raw_spinlock_t *lock)
@@ -127,10 +127,10 @@ static __always_inline void __ticket_spin_lock(raw_spinlock_t *lock)
: "memory", "cc");
}

-static __always_inline int __ticket_spin_trylock(raw_spinlock_t *lock)
+static __always_inline bool __ticket_spin_trylock(raw_spinlock_t *lock)
{
int tmp;
- int new;
+ union { int i; bool b; } new;

asm volatile("movl %2,%0\n\t"
"movl %0,%1\n\t"
@@ -141,12 +141,11 @@ static __always_inline int __ticket_spin_trylock(raw_spinlock_t *lock)
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.b;
}

static __always_inline void __ticket_spin_unlock(raw_spinlock_t *lock)
@@ -190,7 +189,7 @@ static __always_inline void __raw_spin_lock(raw_spinlock_t *lock)
__ticket_spin_lock(lock);
}

-static __always_inline int __raw_spin_trylock(raw_spinlock_t *lock)
+static __always_inline bool __raw_spin_trylock(raw_spinlock_t *lock)
{
return __ticket_spin_trylock(lock);
}
diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
index 36a5141..5d2e67e 100644
--- a/arch/x86/xen/spinlock.c
+++ b/arch/x86/xen/spinlock.c
@@ -136,7 +136,7 @@ static int xen_spin_is_contended(struct raw_spinlock *lock)
return xl->spinners != 0;
}

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

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