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Diffstat (limited to 'include/asm-x86/spinlock_64.h')
| -rw-r--r-- | include/asm-x86/spinlock_64.h | 167 |
1 files changed, 167 insertions, 0 deletions
diff --git a/include/asm-x86/spinlock_64.h b/include/asm-x86/spinlock_64.h new file mode 100644 index 000000000000..88bf981e73cf --- /dev/null +++ b/include/asm-x86/spinlock_64.h @@ -0,0 +1,167 @@ +#ifndef __ASM_SPINLOCK_H +#define __ASM_SPINLOCK_H + +#include <asm/atomic.h> +#include <asm/rwlock.h> +#include <asm/page.h> +#include <asm/processor.h> + +/* + * Your basic SMP spinlocks, allowing only a single CPU anywhere + * + * Simple spin lock operations. There are two variants, one clears IRQ's + * on the local processor, one does not. + * + * We make no fairness assumptions. They have a cost. + * + * (the type definitions are in asm/spinlock_types.h) + */ + +static inline int __raw_spin_is_locked(raw_spinlock_t *lock) +{ + return *(volatile signed int *)(&(lock)->slock) <= 0; +} + +static inline void __raw_spin_lock(raw_spinlock_t *lock) +{ + asm volatile( + "\n1:\t" + LOCK_PREFIX " ; decl %0\n\t" + "jns 2f\n" + "3:\n" + "rep;nop\n\t" + "cmpl $0,%0\n\t" + "jle 3b\n\t" + "jmp 1b\n" + "2:\t" : "=m" (lock->slock) : : "memory"); +} + +/* + * Same as __raw_spin_lock, but reenable interrupts during spinning. + */ +#ifndef CONFIG_PROVE_LOCKING +static inline void __raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long flags) +{ + asm volatile( + "\n1:\t" + LOCK_PREFIX " ; decl %0\n\t" + "jns 5f\n" + "testl $0x200, %1\n\t" /* interrupts were disabled? */ + "jz 4f\n\t" + "sti\n" + "3:\t" + "rep;nop\n\t" + "cmpl $0, %0\n\t" + "jle 3b\n\t" + "cli\n\t" + "jmp 1b\n" + "4:\t" + "rep;nop\n\t" + "cmpl $0, %0\n\t" + "jg 1b\n\t" + "jmp 4b\n" + "5:\n\t" + : "+m" (lock->slock) : "r" ((unsigned)flags) : "memory"); +} +#endif + +static inline int __raw_spin_trylock(raw_spinlock_t *lock) +{ + int oldval; + + asm volatile( + "xchgl %0,%1" + :"=q" (oldval), "=m" (lock->slock) + :"0" (0) : "memory"); + + return oldval > 0; +} + +static inline void __raw_spin_unlock(raw_spinlock_t *lock) +{ + asm volatile("movl $1,%0" :"=m" (lock->slock) :: "memory"); +} + +static inline void __raw_spin_unlock_wait(raw_spinlock_t *lock) +{ + while (__raw_spin_is_locked(lock)) + cpu_relax(); +} + +/* + * Read-write spinlocks, allowing multiple readers + * but only one writer. + * + * NOTE! it is quite common to have readers in interrupts + * but no interrupt writers. For those circumstances we + * can "mix" irq-safe locks - any writer needs to get a + * irq-safe write-lock, but readers can get non-irqsafe + * read-locks. + * + * On x86, we implement read-write locks as a 32-bit counter + * with the high bit (sign) being the "contended" bit. + */ + +static inline int __raw_read_can_lock(raw_rwlock_t *lock) +{ + return (int)(lock)->lock > 0; +} + +static inline int __raw_write_can_lock(raw_rwlock_t *lock) +{ + return (lock)->lock == RW_LOCK_BIAS; +} + +static inline void __raw_read_lock(raw_rwlock_t *rw) +{ + asm volatile(LOCK_PREFIX "subl $1,(%0)\n\t" + "jns 1f\n" + "call __read_lock_failed\n" + "1:\n" + ::"D" (rw), "i" (RW_LOCK_BIAS) : "memory"); +} + +static inline void __raw_write_lock(raw_rwlock_t *rw) +{ + asm volatile(LOCK_PREFIX "subl %1,(%0)\n\t" + "jz 1f\n" + "\tcall __write_lock_failed\n\t" + "1:\n" + ::"D" (rw), "i" (RW_LOCK_BIAS) : "memory"); +} + +static inline int __raw_read_trylock(raw_rwlock_t *lock) +{ + atomic_t *count = (atomic_t *)lock; + atomic_dec(count); + if (atomic_read(count) >= 0) + return 1; + atomic_inc(count); + return 0; +} + +static inline int __raw_write_trylock(raw_rwlock_t *lock) +{ + atomic_t *count = (atomic_t *)lock; + if (atomic_sub_and_test(RW_LOCK_BIAS, count)) + return 1; + atomic_add(RW_LOCK_BIAS, count); + return 0; +} + +static inline void __raw_read_unlock(raw_rwlock_t *rw) +{ + asm volatile(LOCK_PREFIX " ; incl %0" :"=m" (rw->lock) : : "memory"); +} + +static inline void __raw_write_unlock(raw_rwlock_t *rw) +{ + asm volatile(LOCK_PREFIX " ; addl $" RW_LOCK_BIAS_STR ",%0" + : "=m" (rw->lock) : : "memory"); +} + +#define _raw_spin_relax(lock) cpu_relax() +#define _raw_read_relax(lock) cpu_relax() +#define _raw_write_relax(lock) cpu_relax() + +#endif /* __ASM_SPINLOCK_H */ |