atomic.h

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/*
 *  arch/arm/include/asm/atomic.h
 *
 *  Copyright (C) 1996 Russell King.
 *  Copyright (C) 2002 Deep Blue Solutions Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#ifndef __ASM_ARM_ATOMIC_H
#define __ASM_ARM_ATOMIC_H

#include <linux/compiler.h>
#include <linux/types.h>
#include <linux/irqflags.h>
#include <asm/barrier.h>
#include <asm/cmpxchg.h>

#define ATOMIC_INIT(i)  { (i) }

#ifdef __KERNEL__

/*
 * On ARM, ordinary assignment (str instruction) doesn't clear the local
 * strex/ldrex monitor on some implementations. The reason we can use it for
 * atomic_set() is the clrex or dummy strex done on every exception return.
 */
#define atomic_read(v)  (*(volatile int *)&(v)->counter)
#define atomic_set(v,i) (((v)->counter) = (i))

#if __LINUX_ARM_ARCH__ >= 6

/*
 * ARMv6 UP and SMP safe atomic ops.  We use load exclusive and
 * store exclusive to ensure that these are atomic.  We may loop
 * to ensure that the update happens.
 */
static inline void atomic_add(int i, atomic_t *v)
{
    unsigned long tmp;
    int result;

    __asm__ __volatile__("@ atomic_add\n"
"1: ldrex   %0, [%3]\n"
"   add %0, %0, %4\n"
"   strex   %1, %0, [%3]\n"
"   teq %1, #0\n"
"   bne 1b"
    : "=&r" (result), "=&r" (tmp), "+Qo" (v->counter)
    : "r" (&v->counter), "Ir" (i)
    : "cc");
}

static inline int atomic_add_return(int i, atomic_t *v)
{
    unsigned long tmp;
    int result;

    smp_mb();

    __asm__ __volatile__("@ atomic_add_return\n"
"1: ldrex   %0, [%3]\n"
"   add %0, %0, %4\n"
"   strex   %1, %0, [%3]\n"
"   teq %1, #0\n"
"   bne 1b"
    : "=&r" (result), "=&r" (tmp), "+Qo" (v->counter)
    : "r" (&v->counter), "Ir" (i)
    : "cc");

    smp_mb();

    return result;
}

static inline void atomic_sub(int i, atomic_t *v)
{
    unsigned long tmp;
    int result;

    __asm__ __volatile__("@ atomic_sub\n"
"1: ldrex   %0, [%3]\n"
"   sub %0, %0, %4\n"
"   strex   %1, %0, [%3]\n"
"   teq %1, #0\n"
"   bne 1b"
    : "=&r" (result), "=&r" (tmp), "+Qo" (v->counter)
    : "r" (&v->counter), "Ir" (i)
    : "cc");
}

static inline int atomic_sub_return(int i, atomic_t *v)
{
    unsigned long tmp;
    int result;

    smp_mb();

    __asm__ __volatile__("@ atomic_sub_return\n"
"1: ldrex   %0, [%3]\n"
"   sub %0, %0, %4\n"
"   strex   %1, %0, [%3]\n"
"   teq %1, #0\n"
"   bne 1b"
    : "=&r" (result), "=&r" (tmp), "+Qo" (v->counter)
    : "r" (&v->counter), "Ir" (i)
    : "cc");

    smp_mb();

    return result;
}

static inline int atomic_cmpxchg(atomic_t *ptr, int old, int new)
{
    unsigned long oldval, res;

    smp_mb();

    do {
        __asm__ __volatile__("@ atomic_cmpxchg\n"
        "ldrex  %1, [%3]\n"
        "mov    %0, #0\n"
        "teq    %1, %4\n"
        "strexeq %0, %5, [%3]\n"
            : "=&r" (res), "=&r" (oldval), "+Qo" (ptr->counter)
            : "r" (&ptr->counter), "Ir" (old), "r" (new)
            : "cc");
    } while (res);

    smp_mb();

    return oldval;
}

static inline void atomic_clear_mask(unsigned long mask, unsigned long *addr)
{
    unsigned long tmp, tmp2;

    __asm__ __volatile__("@ atomic_clear_mask\n"
"1: ldrex   %0, [%3]\n"
"   bic %0, %0, %4\n"
"   strex   %1, %0, [%3]\n"
"   teq %1, #0\n"
"   bne 1b"
    : "=&r" (tmp), "=&r" (tmp2), "+Qo" (*addr)
    : "r" (addr), "Ir" (mask)
    : "cc");
}

#else /* ARM_ARCH_6 */

#ifdef CONFIG_SMP
#error SMP not supported on pre-ARMv6 CPUs
#endif

static inline int atomic_add_return(int i, atomic_t *v)
{
    unsigned long flags;
    int val;

    raw_local_irq_save(flags);
    val = v->counter;
    v->counter = val += i;
    raw_local_irq_restore(flags);

    return val;
}
#define atomic_add(i, v)    (void) atomic_add_return(i, v)

static inline int atomic_sub_return(int i, atomic_t *v)
{
    unsigned long flags;
    int val;

    raw_local_irq_save(flags);
    val = v->counter;
    v->counter = val -= i;
    raw_local_irq_restore(flags);

    return val;
}
#define atomic_sub(i, v)    (void) atomic_sub_return(i, v)

static inline int atomic_cmpxchg(atomic_t *v, int old, int new)
{
    int ret;
    unsigned long flags;

    raw_local_irq_save(flags);
    ret = v->counter;
    if (likely(ret == old))
        v->counter = new;
    raw_local_irq_restore(flags);

    return ret;
}

static inline void atomic_clear_mask(unsigned long mask, unsigned long *addr)
{
    unsigned long flags;

    raw_local_irq_save(flags);
    *addr &= ~mask;
    raw_local_irq_restore(flags);
}

#endif /* __LINUX_ARM_ARCH__ */

#define atomic_xchg(v, new) (xchg(&((v)->counter), new))

static inline int __atomic_add_unless(atomic_t *v, int a, int u)
{
    int c, old;

    c = atomic_read(v);
    while (c != u && (old = atomic_cmpxchg((v), c, c + a)) != c)
        c = old;
    return c;
}

#define atomic_inc(v)       atomic_add(1, v)
#define atomic_dec(v)       atomic_sub(1, v)

#define atomic_inc_and_test(v)  (atomic_add_return(1, v) == 0)
#define atomic_dec_and_test(v)  (atomic_sub_return(1, v) == 0)
#define atomic_inc_return(v)    (atomic_add_return(1, v))
#define atomic_dec_return(v)    (atomic_sub_return(1, v))
#define atomic_sub_and_test(i, v) (atomic_sub_return(i, v) == 0)

#define atomic_add_negative(i,v) (atomic_add_return(i, v) < 0)

#define smp_mb__before_atomic_dec() smp_mb()
#define smp_mb__after_atomic_dec()  smp_mb()
#define smp_mb__before_atomic_inc() smp_mb()
#define smp_mb__after_atomic_inc()  smp_mb()

#ifndef CONFIG_GENERIC_ATOMIC64
typedef struct {
    u64 __aligned(8) counter;
} atomic64_t;

#define ATOMIC64_INIT(i) { (i) }

static inline u64 atomic64_read(const atomic64_t *v)
{
    u64 result;

    __asm__ __volatile__("@ atomic64_read\n"
"   ldrexd  %0, %H0, [%1]"
    : "=&r" (result)
    : "r" (&v->counter), "Qo" (v->counter)
    );

    return result;
}

static inline void atomic64_set(atomic64_t *v, u64 i)
{
    u64 tmp;

    __asm__ __volatile__("@ atomic64_set\n"
"1: ldrexd  %0, %H0, [%2]\n"
"   strexd  %0, %3, %H3, [%2]\n"
"   teq %0, #0\n"
"   bne 1b"
    : "=&r" (tmp), "=Qo" (v->counter)
    : "r" (&v->counter), "r" (i)
    : "cc");
}

static inline void atomic64_add(u64 i, atomic64_t *v)
{
    u64 result;
    unsigned long tmp;

    __asm__ __volatile__("@ atomic64_add\n"
"1: ldrexd  %0, %H0, [%3]\n"
"   adds    %0, %0, %4\n"
"   adc %H0, %H0, %H4\n"
"   strexd  %1, %0, %H0, [%3]\n"
"   teq %1, #0\n"
"   bne 1b"
    : "=&r" (result), "=&r" (tmp), "+Qo" (v->counter)
    : "r" (&v->counter), "r" (i)
    : "cc");
}

static inline u64 atomic64_add_return(u64 i, atomic64_t *v)
{
    u64 result;
    unsigned long tmp;

    smp_mb();

    __asm__ __volatile__("@ atomic64_add_return\n"
"1: ldrexd  %0, %H0, [%3]\n"
"   adds    %0, %0, %4\n"
"   adc %H0, %H0, %H4\n"
"   strexd  %1, %0, %H0, [%3]\n"
"   teq %1, #0\n"
"   bne 1b"
    : "=&r" (result), "=&r" (tmp), "+Qo" (v->counter)
    : "r" (&v->counter), "r" (i)
    : "cc");

    smp_mb();

    return result;
}

static inline void atomic64_sub(u64 i, atomic64_t *v)
{
    u64 result;
    unsigned long tmp;

    __asm__ __volatile__("@ atomic64_sub\n"
"1: ldrexd  %0, %H0, [%3]\n"
"   subs    %0, %0, %4\n"
"   sbc %H0, %H0, %H4\n"
"   strexd  %1, %0, %H0, [%3]\n"
"   teq %1, #0\n"
"   bne 1b"
    : "=&r" (result), "=&r" (tmp), "+Qo" (v->counter)
    : "r" (&v->counter), "r" (i)
    : "cc");
}

static inline u64 atomic64_sub_return(u64 i, atomic64_t *v)
{
    u64 result;
    unsigned long tmp;

    smp_mb();

    __asm__ __volatile__("@ atomic64_sub_return\n"
"1: ldrexd  %0, %H0, [%3]\n"
"   subs    %0, %0, %4\n"
"   sbc %H0, %H0, %H4\n"
"   strexd  %1, %0, %H0, [%3]\n"
"   teq %1, #0\n"
"   bne 1b"
    : "=&r" (result), "=&r" (tmp), "+Qo" (v->counter)
    : "r" (&v->counter), "r" (i)
    : "cc");

    smp_mb();

    return result;
}

static inline u64 atomic64_cmpxchg(atomic64_t *ptr, u64 old, u64 new)
{
    u64 oldval;
    unsigned long res;

    smp_mb();

    do {
        __asm__ __volatile__("@ atomic64_cmpxchg\n"
        "ldrexd     %1, %H1, [%3]\n"
        "mov        %0, #0\n"
        "teq        %1, %4\n"
        "teqeq      %H1, %H4\n"
        "strexdeq   %0, %5, %H5, [%3]"
        : "=&r" (res), "=&r" (oldval), "+Qo" (ptr->counter)
        : "r" (&ptr->counter), "r" (old), "r" (new)
        : "cc");
    } while (res);

    smp_mb();

    return oldval;
}

static inline u64 atomic64_xchg(atomic64_t *ptr, u64 new)
{
    u64 result;
    unsigned long tmp;

    smp_mb();

    __asm__ __volatile__("@ atomic64_xchg\n"
"1: ldrexd  %0, %H0, [%3]\n"
"   strexd  %1, %4, %H4, [%3]\n"
"   teq %1, #0\n"
"   bne 1b"
    : "=&r" (result), "=&r" (tmp), "+Qo" (ptr->counter)
    : "r" (&ptr->counter), "r" (new)
    : "cc");

    smp_mb();

    return result;
}

static inline u64 atomic64_dec_if_positive(atomic64_t *v)
{
    u64 result;
    unsigned long tmp;

    smp_mb();

    __asm__ __volatile__("@ atomic64_dec_if_positive\n"
"1: ldrexd  %0, %H0, [%3]\n"
"   subs    %0, %0, #1\n"
"   sbc %H0, %H0, #0\n"
"   teq %H0, #0\n"
"   bmi 2f\n"
"   strexd  %1, %0, %H0, [%3]\n"
"   teq %1, #0\n"
"   bne 1b\n"
"2:"
    : "=&r" (result), "=&r" (tmp), "+Qo" (v->counter)
    : "r" (&v->counter)
    : "cc");

    smp_mb();

    return result;
}

static inline int atomic64_add_unless(atomic64_t *v, u64 a, u64 u)
{
    u64 val;
    unsigned long tmp;
    int ret = 1;

    smp_mb();

    __asm__ __volatile__("@ atomic64_add_unless\n"
"1: ldrexd  %0, %H0, [%4]\n"
"   teq %0, %5\n"
"   teqeq   %H0, %H5\n"
"   moveq   %1, #0\n"
"   beq 2f\n"
"   adds    %0, %0, %6\n"
"   adc %H0, %H0, %H6\n"
"   strexd  %2, %0, %H0, [%4]\n"
"   teq %2, #0\n"
"   bne 1b\n"
"2:"
    : "=&r" (val), "+r" (ret), "=&r" (tmp), "+Qo" (v->counter)
    : "r" (&v->counter), "r" (u), "r" (a)
    : "cc");

    if (ret)
        smp_mb();

    return ret;
}

#define atomic64_add_negative(a, v) (atomic64_add_return((a), (v)) < 0)
#define atomic64_inc(v)         atomic64_add(1LL, (v))
#define atomic64_inc_return(v)      atomic64_add_return(1LL, (v))
#define atomic64_inc_and_test(v)    (atomic64_inc_return(v) == 0)
#define atomic64_sub_and_test(a, v) (atomic64_sub_return((a), (v)) == 0)
#define atomic64_dec(v)         atomic64_sub(1LL, (v))
#define atomic64_dec_return(v)      atomic64_sub_return(1LL, (v))
#define atomic64_dec_and_test(v)    (atomic64_dec_return((v)) == 0)
#define atomic64_inc_not_zero(v)    atomic64_add_unless((v), 1LL, 0LL)

#endif /* !CONFIG_GENERIC_ATOMIC64 */
#endif
#endif