LXR linux/arch/ia64/include/asm/mutex.h

   1/*
   2 * ia64 implementation of the mutex fastpath.
   3 *
   4 * Copyright (C) 2006 Ken Chen <kenneth.w.chen@intel.com>
   5 *
   6 */
   7
   8#ifndef _ASM_MUTEX_H
   9#define _ASM_MUTEX_H
  10
  11/**
  12 *  __mutex_fastpath_lock - try to take the lock by moving the count
  13 *                          from 1 to a 0 value
  14 *  @count: pointer of type atomic_t
  15 *  @fail_fn: function to call if the original value was not 1
  16 *
  17 * Change the count from 1 to a value lower than 1, and call <fail_fn> if
  18 * it wasn't 1 originally. This function MUST leave the value lower than
  19 * 1 even when the "1" assertion wasn't true.
  20 */
  21static inline void
  22__mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *))
  23{
  24        if (unlikely(ia64_fetchadd4_acq(count, -1) != 1))
  25                fail_fn(count);
  26}
  27
  28/**
  29 *  __mutex_fastpath_lock_retval - try to take the lock by moving the count
  30 *                                 from 1 to a 0 value
  31 *  @count: pointer of type atomic_t
  32 *
  33 * Change the count from 1 to a value lower than 1. This function returns 0
  34 * if the fastpath succeeds, or -1 otherwise.
  35 */
  36static inline int
  37__mutex_fastpath_lock_retval(atomic_t *count)
  38{
  39        if (unlikely(ia64_fetchadd4_acq(count, -1) != 1))
  40                return -1;
  41        return 0;
  42}
  43
  44/**
  45 *  __mutex_fastpath_unlock - try to promote the count from 0 to 1
  46 *  @count: pointer of type atomic_t
  47 *  @fail_fn: function to call if the original value was not 0
  48 *
  49 * Try to promote the count from 0 to 1. If it wasn't 0, call <fail_fn>.
  50 * In the failure case, this function is allowed to either set the value to
  51 * 1, or to set it to a value lower than 1.
  52 *
  53 * If the implementation sets it to a value of lower than 1, then the
  54 * __mutex_slowpath_needs_to_unlock() macro needs to return 1, it needs
  55 * to return 0 otherwise.
  56 */
  57static inline void
  58__mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
  59{
  60        int ret = ia64_fetchadd4_rel(count, 1);
  61        if (unlikely(ret < 0))
  62                fail_fn(count);
  63}
  64
  65#define __mutex_slowpath_needs_to_unlock()              1
  66
  67/**
  68 * __mutex_fastpath_trylock - try to acquire the mutex, without waiting
  69 *
  70 *  @count: pointer of type atomic_t
  71 *  @fail_fn: fallback function
  72 *
  73 * Change the count from 1 to a value lower than 1, and return 0 (failure)
  74 * if it wasn't 1 originally, or return 1 (success) otherwise. This function
  75 * MUST leave the value lower than 1 even when the "1" assertion wasn't true.
  76 * Additionally, if the value was < 0 originally, this function must not leave
  77 * it to 0 on failure.
  78 *
  79 * If the architecture has no effective trylock variant, it should call the
  80 * <fail_fn> spinlock-based trylock variant unconditionally.
  81 */
  82static inline int
  83__mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
  84{
  85        if (cmpxchg_acq(count, 1, 0) == 1)
  86                return 1;
  87        return 0;
  88}
  89
  90#endif
  91