mutex_64.h

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/*
 * Assembly implementation of the mutex fastpath, based on atomic
 * decrement/increment.
 *
 * started by Ingo Molnar:
 *
 *  Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <[email protected]>
 */
#ifndef _ASM_X86_MUTEX_64_H
#define _ASM_X86_MUTEX_64_H

#define __mutex_fastpath_lock(v, fail_fn)           \
do {                                \
    unsigned long dummy;                    \
                                \
    typecheck(atomic_t *, v);               \
    typecheck_fn(void (*)(atomic_t *), fail_fn);        \
                                \
    asm volatile(LOCK_PREFIX "   decl (%%rdi)\n"        \
             "   jns 1f     \n"         \
             "   call " #fail_fn "\n"           \
             "1:"                   \
             : "=D" (dummy)             \
             : "D" (v)                  \
             : "rax", "rsi", "rdx", "rcx",      \
               "r8", "r9", "r10", "r11", "memory"); \
} while (0)

static inline int __mutex_fastpath_lock_retval(atomic_t *count,
                           int (*fail_fn)(atomic_t *))
{
    if (unlikely(atomic_dec_return(count) < 0))
        return fail_fn(count);
    else
        return 0;
}

#define __mutex_fastpath_unlock(v, fail_fn)         \
do {                                \
    unsigned long dummy;                    \
                                \
    typecheck(atomic_t *, v);               \
    typecheck_fn(void (*)(atomic_t *), fail_fn);        \
                                \
    asm volatile(LOCK_PREFIX "   incl (%%rdi)\n"        \
             "   jg 1f\n"               \
             "   call " #fail_fn "\n"           \
             "1:"                   \
             : "=D" (dummy)             \
             : "D" (v)                  \
             : "rax", "rsi", "rdx", "rcx",      \
               "r8", "r9", "r10", "r11", "memory"); \
} while (0)

#define __mutex_slowpath_needs_to_unlock()  1

static inline int __mutex_fastpath_trylock(atomic_t *count,
                       int (*fail_fn)(atomic_t *))
{
    if (likely(atomic_cmpxchg(count, 1, 0) == 1))
        return 1;
    else
        return 0;
}

#endif /* _ASM_X86_MUTEX_64_H */