text: #ifndef _ASM_IA64_SPINLOCK_H
  #define _ASM_IA64_SPINLOCK_H
  
  /*
   * Copyright (C) 1998-2003 Hewlett-Packard Co
   *	David Mosberger-Tang <davidm@hpl.hp.com>
   * Copyright (C) 1999 Walt Drummond <drummond@valinux.com>
   *
   * This file is used for SMP configurations only.
   */
  
  #include <linux/compiler.h>
  #include <linux/kernel.h>
  #include <linux/bitops.h>
  
  #include <linux/atomic.h>
  #include <asm/intrinsics.h>
  #include <asm/system.h>
  
  #define arch_spin_lock_init(x)			((x)->lock = 0)
  
  /*
   * Ticket locks are conceptually two parts, one indicating the current head of
   * the queue, and the other indicating the current tail. The lock is acquired
   * by atomically noting the tail and incrementing it by one (thus adding
   * ourself to the queue and noting our position), then waiting until the head
   * becomes equal to the the initial value of the tail.
   * The pad bits in the middle are used to prevent the next_ticket number
   * overflowing into the now_serving number.
   *
   *   31             17  16    15  14                    0
   *  +----------------------------------------------------+
   *  |  now_serving     | padding |   next_ticket         |
   *  +----------------------------------------------------+
   */
  
  #define TICKET_SHIFT	17
  #define TICKET_BITS	15
  #define	TICKET_MASK	((1 << TICKET_BITS) - 1)
  
  static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock)
  {
  	int	*p = (int *)&lock->lock, ticket, serve;
  
  	ticket = ia64_fetchadd(1, p, acq);
  
  	if (!(((ticket >> TICKET_SHIFT) ^ ticket) & TICKET_MASK))
  		return;
  
  	ia64_invala();
  
  	for (;;) {
  		asm volatile ("ld4.c.nc %0=[%1]" : "=r"(serve) : "r"(p) : "memory");
  
  		if (!(((serve >> TICKET_SHIFT) ^ ticket) & TICKET_MASK))
  			return;
  		cpu_relax();
  	}
  }
  
  static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)
  {
  	int tmp = ACCESS_ONCE(lock->lock);
  
  	if (!(((tmp >> TICKET_SHIFT) ^ tmp) & TICKET_MASK))
  		return ia64_cmpxchg(acq, &lock->lock, tmp, tmp + 1, sizeof (tmp)) == tmp;
  	return 0;
  }
  
  static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock)
  {
  	unsigned short	*p = (unsigned short *)&lock->lock + 1, tmp;
  
  	asm volatile ("ld2.bias %0=[%1]" : "=r"(tmp) : "r"(p));
  	ACCESS_ONCE(*p) = (tmp + 2) & ~1;
  }
  
  static __always_inline void __ticket_spin_unlock_wait(arch_spinlock_t *lock)
  {
  	int	*p = (int *)&lock->lock, ticket;
  
  	ia64_invala();
  
  	for (;;) {
  		asm volatile ("ld4.c.nc %0=[%1]" : "=r"(ticket) : "r"(p) : "memory");
  		if (!(((ticket >> TICKET_SHIFT) ^ ticket) & TICKET_MASK))
  			return;
  		cpu_relax();
  	}
  }
  
  static inline int __ticket_spin_is_locked(arch_spinlock_t *lock)
  {
  	long tmp = ACCESS_ONCE(lock->lock);
  
  	return !!(((tmp >> TICKET_SHIFT) ^ tmp) & TICKET_MASK);
  }
  
  static inline int __ticket_spin_is_contended(arch_spinlock_t *lock)
  {
  	long tmp = ACCESS_ONCE(lock->lock);
  
  	return ((tmp - (tmp >> TICKET_SHIFT)) & TICKET_MASK) > 1;
  }
  
  static inline int arch_spin_is_locked(arch_spinlock_t *lock)
  {
  	return __ticket_spin_is_locked(lock);
  }
  
  static inline int arch_spin_is_contended(arch_spinlock_t *lock)
  {
  	return __ticket_spin_is_contended(lock);
  }
  #define arch_spin_is_contended	arch_spin_is_contended
  
  static __always_inline void arch_spin_lock(arch_spinlock_t *lock)
  {
  	__ticket_spin_lock(lock);
  }
  
  static __always_inline int arch_spin_trylock(arch_spinlock_t *lock)
  {
  	return __ticket_spin_trylock(lock);
  }
  
  static __always_inline void arch_spin_unlock(arch_spinlock_t *lock)
  {
  	__ticket_spin_unlock(lock);
  }
  
  static __always_inline void arch_spin_lock_flags(arch_spinlock_t *lock,
  						  unsigned long flags)
  {
  	arch_spin_lock(lock);
  }
  
  static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
  {
  	__ticket_spin_unlock_wait(lock);
  }
  
  #define arch_read_can_lock(rw)		(*(volatile int *)(rw) >= 0)
  #define arch_write_can_lock(rw)	(*(volatile int *)(rw) == 0)
  
  #ifdef ASM_SUPPORTED
  
  static __always_inline void
  arch_read_lock_flags(arch_rwlock_t *lock, unsigned long flags)
  {
  	__asm__ __volatile__ (
  		"tbit.nz p6, p0 = %1,%2\n"
  		"br.few 3f\n"
  		"1:\n"
  		"fetchadd4.rel r2 = [%0], -1;;\n"
  		"(p6) ssm psr.i\n"
  		"2:\n"
  		"hint @pause\n"
  		"ld4 r2 = [%0];;\n"
  		"cmp4.lt p7,p0 = r2, r0\n"
  		"(p7) br.cond.spnt.few 2b\n"
  		"(p6) rsm psr.i\n"
  		";;\n"
  		"3:\n"
  		"fetchadd4.acq r2 = [%0], 1;;\n"
  		"cmp4.lt p7,p0 = r2, r0\n"
  		"(p7) br.cond.spnt.few 1b\n"
  		: : "r"(lock), "r"(flags), "i"(IA64_PSR_I_BIT)
  		: "p6", "p7", "r2", "memory");
  }
  
  #define arch_read_lock(lock) arch_read_lock_flags(lock, 0)
  
  #else /* !ASM_SUPPORTED */
  
  #define arch_read_lock_flags(rw, flags) arch_read_lock(rw)
  
  #define arch_read_lock(rw)								\
  do {											\
  	arch_rwlock_t *__read_lock_ptr = (rw);						\
  											\
  	while (unlikely(ia64_fetchadd(1, (int *) __read_lock_ptr, acq) < 0)) {		\
  		ia64_fetchadd(-1, (int *) __read_lock_ptr, rel);			\
  		while (*(volatile int *)__read_lock_ptr < 0)				\
  			cpu_relax();							\
  	}										\
  } while (0)
  
  #endif /* !ASM_SUPPORTED */
  
  #define arch_read_unlock(rw)					\
  do {								\
  	arch_rwlock_t *__read_lock_ptr = (rw);			\
  	ia64_fetchadd(-1, (int *) __read_lock_ptr, rel);	\
  } while (0)
  
  #ifdef ASM_SUPPORTED
  
  static __always_inline void
  arch_write_lock_flags(arch_rwlock_t *lock, unsigned long flags)
  {
  	__asm__ __volatile__ (
  		"tbit.nz p6, p0 = %1, %2\n"
  		"mov ar.ccv = r0\n"
  		"dep r29 = -1, r0, 31, 1\n"
  		"br.few 3f;;\n"
  		"1:\n"
  		"(p6) ssm psr.i\n"
  		"2:\n"
  		"hint @pause\n"
  		"ld4 r2 = [%0];;\n"
  		"cmp4.eq p0,p7 = r0, r2\n"
  		"(p7) br.cond.spnt.few 2b\n"
  		"(p6) rsm psr.i\n"
  		";;\n"
  		"3:\n"
  		"cmpxchg4.acq r2 = [%0], r29, ar.ccv;;\n"
  		"cmp4.eq p0,p7 = r0, r2\n"
  		"(p7) br.cond.spnt.few 1b;;\n"
  		: : "r"(lock), "r"(flags), "i"(IA64_PSR_I_BIT)
  		: "ar.ccv", "p6", "p7", "r2", "r29", "memory");
  }
  
  #define arch_write_lock(rw) arch_write_lock_flags(rw, 0)
  
  #define arch_write_trylock(rw)							\
  ({										\
  	register long result;							\
  										\
  	__asm__ __volatile__ (							\
  		"mov ar.ccv = r0\n"						\
  		"dep r29 = -1, r0, 31, 1;;\n"					\
  		"cmpxchg4.acq %0 = [%1], r29, ar.ccv\n"				\
  		: "=r"(result) : "r"(rw) : "ar.ccv", "r29", "memory");		\
  	(result == 0);								\
  })
  
  static inline void arch_write_unlock(arch_rwlock_t *x)
  {
  	u8 *y = (u8 *)x;
  	barrier();
  	asm volatile ("st1.rel.nta [%0] = r0\n\t" :: "r"(y+3) : "memory" );
  }
  
  #else /* !ASM_SUPPORTED */
  
  #define arch_write_lock_flags(l, flags) arch_write_lock(l)
  
  #define arch_write_lock(l)								\
  ({											\
  	__u64 ia64_val, ia64_set_val = ia64_dep_mi(-1, 0, 31, 1);			\
  	__u32 *ia64_write_lock_ptr = (__u32 *) (l);					\
  	do {										\
  		while (*ia64_write_lock_ptr)						\
  			ia64_barrier();							\
  		ia64_val = ia64_cmpxchg4_acq(ia64_write_lock_ptr, ia64_set_val, 0);	\
  	} while (ia64_val);								\
  })
  
  #define arch_write_trylock(rw)						\
  ({									\
  	__u64 ia64_val;							\
  	__u64 ia64_set_val = ia64_dep_mi(-1, 0, 31,1);			\
  	ia64_val = ia64_cmpxchg4_acq((__u32 *)(rw), ia64_set_val, 0);	\
  	(ia64_val == 0);						\
  })
  
  static inline void arch_write_unlock(arch_rwlock_t *x)
  {
  	barrier();
  	x->write_lock = 0;
  }
  
  #endif /* !ASM_SUPPORTED */
  
  static inline int arch_read_trylock(arch_rwlock_t *x)
  {
  	union {
  		arch_rwlock_t lock;
  		__u32 word;
  	} old, new;
  	old.lock = new.lock = *x;
  	old.lock.write_lock = new.lock.write_lock = 0;
  	++new.lock.read_counter;
  	return (u32)ia64_cmpxchg4_acq((__u32 *)(x), new.word, old.word) == old.word;
  }
  
  #define arch_spin_relax(lock)	cpu_relax()
  #define arch_read_relax(lock)	cpu_relax()
  #define arch_write_relax(lock)	cpu_relax()
  
  #endif /*  _ASM_IA64_SPINLOCK_H */
  