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 *  @fail_fn: function to call if the original value was not 1
  33 *
  34 * Change the count from 1 to a value lower than 1, and call <fail_fn> if
  35 * it wasn't 1 originally. This function returns 0 if the fastpath succeeds,
  36 * or anything the slow path function returns.
  37 */
  38static inline int
  39__mutex_fastpath_lock_retval(atomic_t *count, int (*fail_fn)(atomic_t *))
  40{
  41        if (unlikely(ia64_fetchadd4_acq(count, -1) != 1))
  42                return fail_fn(count);
  43        return 0;
  44}
  45
  46/**
  47 *  __mutex_fastpath_unlock - try to promote the count from 0 to 1
  48 *  @count: pointer of type atomic_t
  49 *  @fail_fn: function to call if the original value was not 0
  50 *
  51 * Try to promote the count from 0 to 1. If it wasn't 0, call <fail_fn>.
  52 * In the failure case, this function is allowed to either set the value to
  53 * 1, or to set it to a value lower than 1.
  54 *
  55 * If the implementation sets it to a value of lower than 1, then the
  56 * __mutex_slowpath_needs_to_unlock() macro needs to return 1, it needs
  57 * to return 0 otherwise.
  58 */
  59static inline void
  60__mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
  61{
  62        int ret = ia64_fetchadd4_rel(count, 1);
  63        if (unlikely(ret < 0))
  64                fail_fn(count);
  65}
  66
  67#define __mutex_slowpath_needs_to_unlock()              1
  68
  69/**
  70 * __mutex_fastpath_trylock - try to acquire the mutex, without waiting
  71 *
  72 *  @count: pointer of type atomic_t
  73 *  @fail_fn: fallback function
  74 *
  75 * Change the count from 1 to a value lower than 1, and return 0 (failure)
  76 * if it wasn't 1 originally, or return 1 (success) otherwise. This function
  77 * MUST leave the value lower than 1 even when the "1" assertion wasn't true.
  78 * Additionally, if the value was < 0 originally, this function must not leave
  79 * it to 0 on failure.
  80 *
  81 * If the architecture has no effective trylock variant, it should call the
  82 * <fail_fn> spinlock-based trylock variant unconditionally.
  83 */
  84static inline int
  85__mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
  86{
  87        if (cmpxchg_acq(count, 1, 0) == 1)
  88                return 1;
  89        return 0;
  90}
  91
  92#endif
  93