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#ifndef __ASM_SPINLOCK_H #define __ASM_SPINLOCK_H #include <asm/atomic.h> #include <asm/rwlock.h> #include <asm/page.h> #include <linux/config.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) */ #define __raw_spin_is_locked(x) \ (*(volatile signed int *)(&(x)->slock) <= 0) #define __raw_spin_lock_string \ "\n1:\t" \ "lock ; decl %0\n\t" \ "js 2f\n" \ LOCK_SECTION_START("") \ "2:\t" \ "rep;nop\n\t" \ "cmpl $0,%0\n\t" \ "jle 2b\n\t" \ "jmp 1b\n" \ LOCK_SECTION_END #define __raw_spin_unlock_string \ "movl $1,%0" \ :"=m" (lock->slock) : : "memory" static inline void __raw_spin_lock(raw_spinlock_t *lock) { __asm__ __volatile__( __raw_spin_lock_string :"=m" (lock->slock) : : "memory"); } #define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock) 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__( __raw_spin_unlock_string ); } #define __raw_spin_unlock_wait(lock) \ do { while (__raw_spin_is_locked(lock)) cpu_relax(); } while (0) /* * 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. * * The inline assembly is non-obvious. Think about it. * * Changed to use the same technique as rw semaphores. See * semaphore.h for details. -ben * * the helpers are in arch/i386/kernel/semaphore.c */ #define __raw_read_can_lock(x) ((int)(x)->lock > 0) #define __raw_write_can_lock(x) ((x)->lock == RW_LOCK_BIAS) static inline void __raw_read_lock(raw_rwlock_t *rw) { __build_read_lock(rw, "__read_lock_failed"); } static inline void __raw_write_lock(raw_rwlock_t *rw) { __build_write_lock(rw, "__write_lock_failed"); } 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 ; incl %0" :"=m" (rw->lock) : : "memory"); } static inline void __raw_write_unlock(raw_rwlock_t *rw) { asm volatile("lock ; addl $" RW_LOCK_BIAS_STR ",%0" : "=m" (rw->lock) : : "memory"); } #endif /* __ASM_SPINLOCK_H */