From afb33f8c0d7dea8c48ae1c2e3af5b437aa8dd7bb Mon Sep 17 00:00:00 2001 From: Jiri Kosina Date: Mon, 12 Jan 2009 12:53:45 +0100 Subject: [PATCH] x86: remove byte locks Impact: cleanup Remove byte locks implementation, which was introduced by Jeremy in 8efcbab6 ("paravirt: introduce a "lock-byte" spinlock implementation"), but turned out to be dead code that is not used by any in-kernel virtualization guest (Xen uses its own variant of spinlocks implementation and KVM is not planning to move to byte locks). Signed-off-by: Jiri Kosina Signed-off-by: Ingo Molnar --- arch/x86/include/asm/paravirt.h | 2 - arch/x86/include/asm/spinlock.h | 66 +--------------------------- arch/x86/kernel/paravirt-spinlocks.c | 10 ----- 3 files changed, 2 insertions(+), 76 deletions(-) diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h index ba3e2ff6aedc..32bc6c2c1386 100644 --- a/arch/x86/include/asm/paravirt.h +++ b/arch/x86/include/asm/paravirt.h @@ -1389,8 +1389,6 @@ static inline void __set_fixmap(unsigned /* enum fixed_addresses */ idx, void _paravirt_nop(void); #define paravirt_nop ((void *)_paravirt_nop) -void paravirt_use_bytelocks(void); - #ifdef CONFIG_SMP static inline int __raw_spin_is_locked(struct raw_spinlock *lock) diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h index d17c91981da2..2bd6b111a414 100644 --- a/arch/x86/include/asm/spinlock.h +++ b/arch/x86/include/asm/spinlock.h @@ -172,70 +172,8 @@ static inline int __ticket_spin_is_contended(raw_spinlock_t *lock) return (((tmp >> TICKET_SHIFT) - tmp) & ((1 << TICKET_SHIFT) - 1)) > 1; } -#ifdef CONFIG_PARAVIRT -/* - * Define virtualization-friendly old-style lock byte lock, for use in - * pv_lock_ops if desired. - * - * This differs from the pre-2.6.24 spinlock by always using xchgb - * rather than decb to take the lock; this allows it to use a - * zero-initialized lock structure. It also maintains a 1-byte - * contention counter, so that we can implement - * __byte_spin_is_contended. - */ -struct __byte_spinlock { - s8 lock; - s8 spinners; -}; - -static inline int __byte_spin_is_locked(raw_spinlock_t *lock) -{ - struct __byte_spinlock *bl = (struct __byte_spinlock *)lock; - return bl->lock != 0; -} - -static inline int __byte_spin_is_contended(raw_spinlock_t *lock) -{ - struct __byte_spinlock *bl = (struct __byte_spinlock *)lock; - return bl->spinners != 0; -} - -static inline void __byte_spin_lock(raw_spinlock_t *lock) -{ - struct __byte_spinlock *bl = (struct __byte_spinlock *)lock; - s8 val = 1; - - asm("1: xchgb %1, %0\n" - " test %1,%1\n" - " jz 3f\n" - " " LOCK_PREFIX "incb %2\n" - "2: rep;nop\n" - " cmpb $1, %0\n" - " je 2b\n" - " " LOCK_PREFIX "decb %2\n" - " jmp 1b\n" - "3:" - : "+m" (bl->lock), "+q" (val), "+m" (bl->spinners): : "memory"); -} - -static inline int __byte_spin_trylock(raw_spinlock_t *lock) -{ - struct __byte_spinlock *bl = (struct __byte_spinlock *)lock; - u8 old = 1; - - asm("xchgb %1,%0" - : "+m" (bl->lock), "+q" (old) : : "memory"); +#ifndef CONFIG_PARAVIRT - return old == 0; -} - -static inline void __byte_spin_unlock(raw_spinlock_t *lock) -{ - struct __byte_spinlock *bl = (struct __byte_spinlock *)lock; - smp_wmb(); - bl->lock = 0; -} -#else /* !CONFIG_PARAVIRT */ static inline int __raw_spin_is_locked(raw_spinlock_t *lock) { return __ticket_spin_is_locked(lock); @@ -267,7 +205,7 @@ static __always_inline void __raw_spin_lock_flags(raw_spinlock_t *lock, __raw_spin_lock(lock); } -#endif /* CONFIG_PARAVIRT */ +#endif static inline void __raw_spin_unlock_wait(raw_spinlock_t *lock) { diff --git a/arch/x86/kernel/paravirt-spinlocks.c b/arch/x86/kernel/paravirt-spinlocks.c index 95777b0faa73..3a7c5a44082e 100644 --- a/arch/x86/kernel/paravirt-spinlocks.c +++ b/arch/x86/kernel/paravirt-spinlocks.c @@ -26,13 +26,3 @@ struct pv_lock_ops pv_lock_ops = { }; EXPORT_SYMBOL(pv_lock_ops); -void __init paravirt_use_bytelocks(void) -{ -#ifdef CONFIG_SMP - pv_lock_ops.spin_is_locked = __byte_spin_is_locked; - pv_lock_ops.spin_is_contended = __byte_spin_is_contended; - pv_lock_ops.spin_lock = __byte_spin_lock; - pv_lock_ops.spin_trylock = __byte_spin_trylock; - pv_lock_ops.spin_unlock = __byte_spin_unlock; -#endif -} -- 2.30.2