diff options
| -rw-r--r-- | arch/x86/kernel/paravirt.c | 9 | ||||
| -rw-r--r-- | include/asm-x86/paravirt.h | 2 | ||||
| -rw-r--r-- | include/asm-x86/spinlock.h | 65 |
3 files changed, 75 insertions, 1 deletions
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c index f3381686870..bba4041bb7f 100644 --- a/arch/x86/kernel/paravirt.c +++ b/arch/x86/kernel/paravirt.c @@ -268,6 +268,15 @@ enum paravirt_lazy_mode paravirt_get_lazy_mode(void) return __get_cpu_var(paravirt_lazy_mode); } +void __init paravirt_use_bytelocks(void) +{ + 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; +} + struct pv_info pv_info = { .name = "bare hardware", .paravirt_enabled = 0, diff --git a/include/asm-x86/paravirt.h b/include/asm-x86/paravirt.h index feb6bb66c5e..65ed02cdbbd 100644 --- a/include/asm-x86/paravirt.h +++ b/include/asm-x86/paravirt.h @@ -1385,6 +1385,8 @@ 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); + static inline int __raw_spin_is_locked(struct raw_spinlock *lock) { return PVOP_CALL1(int, pv_lock_ops.spin_is_locked, lock); diff --git a/include/asm-x86/spinlock.h b/include/asm-x86/spinlock.h index 9726144cdab..4f9a9861799 100644 --- a/include/asm-x86/spinlock.h +++ b/include/asm-x86/spinlock.h @@ -184,7 +184,70 @@ static __always_inline void __ticket_spin_unlock(raw_spinlock_t *lock) #define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock) -#ifndef CONFIG_PARAVIRT +#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"); + + 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); |