source: mainline/kernel/arch/ia32/include/atomic.h@ 0adfc9d

/*
 * Copyright (c) 2001-2004 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup ia32
 * @{
 */
/** @file
 */

#ifndef KERN_ia32_ATOMIC_H_
#define KERN_ia32_ATOMIC_H_

#include <typedefs.h>
#include <arch/barrier.h>
#include <preemption.h>
#include <trace.h>

NO_TRACE static inline void atomic_inc(atomic_t *val)
{
#ifdef CONFIG_SMP
        asm volatile (
                "lock incl %[count]\n"
                : [count] "+m" (val->count)
        );
#else
        asm volatile (
                "incl %[count]\n"
                : [count] "+m" (val->count)
        );
#endif /* CONFIG_SMP */
}

NO_TRACE static inline void atomic_dec(atomic_t *val)
{
#ifdef CONFIG_SMP
        asm volatile (
                "lock decl %[count]\n"
                : [count] "+m" (val->count)
        );
#else
        asm volatile (
                "decl %[count]\n"
                : [count] "+m" (val->count)
        );
#endif /* CONFIG_SMP */
}

NO_TRACE static inline atomic_count_t atomic_postinc(atomic_t *val)
{
        atomic_count_t r = 1;
        
        asm volatile (
                "lock xaddl %[r], %[count]\n"
                : [count] "+m" (val->count),
                  [r] "+r" (r)
        );
        
        return r;
}

NO_TRACE static inline atomic_count_t atomic_postdec(atomic_t *val)
{
        atomic_count_t r = -1;
        
        asm volatile (
                "lock xaddl %[r], %[count]\n"
                : [count] "+m" (val->count),
                  [r] "+r" (r)
        );
        
        return r;
}

#define atomic_preinc(val)  (atomic_postinc(val) + 1)
#define atomic_predec(val)  (atomic_postdec(val) - 1)

NO_TRACE static inline atomic_count_t test_and_set(atomic_t *val)
{
        atomic_count_t v = 1;
        
        asm volatile (
                "xchgl %[v], %[count]\n"
                : [v] "+r" (v),
                  [count] "+m" (val->count)
        );
        
        return v;
}


/** ia32 specific fast spinlock */
NO_TRACE static inline void atomic_lock_arch(atomic_t *val)
{
        atomic_count_t tmp;
        
        preemption_disable();
        asm volatile (
                "0:\n"
#ifndef PROCESSOR_i486
                "pause\n"        /* Pentium 4's HT love this instruction */
#endif
                "mov %[count], %[tmp]\n"
                "testl %[tmp], %[tmp]\n"
                "jnz 0b\n"       /* lightweight looping on locked spinlock */
                
                "incl %[tmp]\n"  /* now use the atomic operation */
                "xchgl %[count], %[tmp]\n"
                "testl %[tmp], %[tmp]\n"
                "jnz 0b\n"
                : [count] "+m" (val->count),
                  [tmp] "=&r" (tmp)
        );
        
        /*
         * Prevent critical section code from bleeding out this way up.
         */
        CS_ENTER_BARRIER();
}


#define _atomic_cas_impl(pptr, exp_val, new_val, old_val, prefix) \
({ \
        switch (sizeof(typeof(*(pptr)))) { \
        case 1: \
                asm volatile ( \
                        prefix " cmpxchgb %[newval], %[ptr]\n" \
                        : /* Output operands. */ \
                        /* Old/current value is returned in eax. */ \
                        [oldval] "=a" (old_val), \
                        /* (*ptr) will be read and written to, hence "+" */ \
                        [ptr] "+m" (*pptr) \
                        : /* Input operands. */ \
                        /* Expected value must be in eax. */ \
                        [expval] "a" (exp_val), \
                        /* The new value may be in any register. */ \
                        [newval] "r" (new_val) \
                        : "memory" \
                ); \
                break; \
        case 2: \
                asm volatile ( \
                        prefix " cmpxchgw %[newval], %[ptr]\n" \
                        : /* Output operands. */ \
                        /* Old/current value is returned in eax. */ \
                        [oldval] "=a" (old_val), \
                        /* (*ptr) will be read and written to, hence "+" */ \
                        [ptr] "+m" (*pptr) \
                        : /* Input operands. */ \
                        /* Expected value must be in eax. */ \
                        [expval] "a" (exp_val), \
                        /* The new value may be in any register. */ \
                        [newval] "r" (new_val) \
                        : "memory" \
                ); \
                break; \
        case 4: \
                asm volatile ( \
                        prefix " cmpxchgl %[newval], %[ptr]\n" \
                        : /* Output operands. */ \
                        /* Old/current value is returned in eax. */ \
                        [oldval] "=a" (old_val), \
                        /* (*ptr) will be read and written to, hence "+" */ \
                        [ptr] "+m" (*pptr) \
                        : /* Input operands. */ \
                        /* Expected value must be in eax. */ \
                        [expval] "a" (exp_val), \
                        /* The new value may be in any register. */ \
                        [newval] "r" (new_val) \
                        : "memory" \
                ); \
                break; \
        } \
})


#ifndef local_atomic_cas

#define local_atomic_cas(pptr, exp_val, new_val) \
({ \
        typeof(*(pptr)) old_val; \
        _atomic_cas_impl(pptr, exp_val, new_val, old_val, ""); \
        \
        old_val; \
})

#else
/* Check if arch/atomic.h does not accidentally include /atomic.h .*/
#error Architecture specific cpu local atomics already defined! Check your includes.
#endif


#ifndef local_atomic_exchange
/* 
 * Issuing a xchg instruction always implies lock prefix semantics.
 * Therefore, it is cheaper to use a cmpxchg without a lock prefix 
 * in a loop.
 */
#define local_atomic_exchange(pptr, new_val) \
({ \
        typeof(*(pptr)) exp_val; \
        typeof(*(pptr)) old_val; \
        \
        do { \
                exp_val = *pptr; \
                old_val = local_atomic_cas(pptr, exp_val, new_val); \
        } while (old_val != exp_val); \
        \
        old_val; \
})

#else
/* Check if arch/atomic.h does not accidentally include /atomic.h .*/
#error Architecture specific cpu local atomics already defined! Check your includes.
#endif


#endif

/** @}
 */