spinlock.h

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#ifndef _ASM_IA64_SPINLOCK_H
#define _ASM_IA64_SPINLOCK_H

/*
 * Copyright (C) 1998-2003 Hewlett-Packard Co
 *  David Mosberger-Tang <[email protected]>
 * Copyright (C) 1999 Walt Drummond <[email protected]>
 *
 * This file is used for SMP configurations only.
 */

#include <linux/compiler.h>
#include <linux/kernel.h>
#include <linux/bitops.h>

#include <linux/atomic.h>
#include <asm/intrinsics.h>

#define arch_spin_lock_init(x)          ((x)->lock = 0)

/*
 * Ticket locks are conceptually two parts, one indicating the current head of
 * the queue, and the other indicating the current tail. The lock is acquired
 * by atomically noting the tail and incrementing it by one (thus adding
 * ourself to the queue and noting our position), then waiting until the head
 * becomes equal to the the initial value of the tail.
 * The pad bits in the middle are used to prevent the next_ticket number
 * overflowing into the now_serving number.
 *
 *   31             17  16    15  14                    0
 *  +----------------------------------------------------+
 *  |  now_serving     | padding |   next_ticket         |
 *  +----------------------------------------------------+
 */

#define TICKET_SHIFT    17
#define TICKET_BITS 15
#define TICKET_MASK ((1 << TICKET_BITS) - 1)

static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock)
{
    int *p = (int *)&lock->lock, ticket, serve;

    ticket = ia64_fetchadd(1, p, acq);

    if (!(((ticket >> TICKET_SHIFT) ^ ticket) & TICKET_MASK))
        return;

    ia64_invala();

    for (;;) {
        asm volatile ("ld4.c.nc %0=[%1]" : "=r"(serve) : "r"(p) : "memory");

        if (!(((serve >> TICKET_SHIFT) ^ ticket) & TICKET_MASK))
            return;
        cpu_relax();
    }
}

static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)
{
    int tmp = ACCESS_ONCE(lock->lock);

    if (!(((tmp >> TICKET_SHIFT) ^ tmp) & TICKET_MASK))
        return ia64_cmpxchg(acq, &lock->lock, tmp, tmp + 1, sizeof (tmp)) == tmp;
    return 0;
}

static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock)
{
    unsigned short  *p = (unsigned short *)&lock->lock + 1, tmp;

    asm volatile ("ld2.bias %0=[%1]" : "=r"(tmp) : "r"(p));
    ACCESS_ONCE(*p) = (tmp + 2) & ~1;
}

static __always_inline void __ticket_spin_unlock_wait(arch_spinlock_t *lock)
{
    int *p = (int *)&lock->lock, ticket;

    ia64_invala();

    for (;;) {
        asm volatile ("ld4.c.nc %0=[%1]" : "=r"(ticket) : "r"(p) : "memory");
        if (!(((ticket >> TICKET_SHIFT) ^ ticket) & TICKET_MASK))
            return;
        cpu_relax();
    }
}

static inline int __ticket_spin_is_locked(arch_spinlock_t *lock)
{
    long tmp = ACCESS_ONCE(lock->lock);

    return !!(((tmp >> TICKET_SHIFT) ^ tmp) & TICKET_MASK);
}

static inline int __ticket_spin_is_contended(arch_spinlock_t *lock)
{
    long tmp = ACCESS_ONCE(lock->lock);

    return ((tmp - (tmp >> TICKET_SHIFT)) & TICKET_MASK) > 1;
}

static inline int arch_spin_is_locked(arch_spinlock_t *lock)
{
    return __ticket_spin_is_locked(lock);
}

static inline int arch_spin_is_contended(arch_spinlock_t *lock)
{
    return __ticket_spin_is_contended(lock);
}
#define arch_spin_is_contended  arch_spin_is_contended

static __always_inline void arch_spin_lock(arch_spinlock_t *lock)
{
    __ticket_spin_lock(lock);
}

static __always_inline int arch_spin_trylock(arch_spinlock_t *lock)
{
    return __ticket_spin_trylock(lock);
}

static __always_inline void arch_spin_unlock(arch_spinlock_t *lock)
{
    __ticket_spin_unlock(lock);
}

static __always_inline void arch_spin_lock_flags(arch_spinlock_t *lock,
                          unsigned long flags)
{
    arch_spin_lock(lock);
}

static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
{
    __ticket_spin_unlock_wait(lock);
}

#define arch_read_can_lock(rw)      (*(volatile int *)(rw) >= 0)
#define arch_write_can_lock(rw) (*(volatile int *)(rw) == 0)

#ifdef ASM_SUPPORTED

static __always_inline void
arch_read_lock_flags(arch_rwlock_t *lock, unsigned long flags)
{
    __asm__ __volatile__ (
        "tbit.nz p6, p0 = %1,%2\n"
        "br.few 3f\n"
        "1:\n"
        "fetchadd4.rel r2 = [%0], -1;;\n"
        "(p6) ssm psr.i\n"
        "2:\n"
        "hint @pause\n"
        "ld4 r2 = [%0];;\n"
        "cmp4.lt p7,p0 = r2, r0\n"
        "(p7) br.cond.spnt.few 2b\n"
        "(p6) rsm psr.i\n"
        ";;\n"
        "3:\n"
        "fetchadd4.acq r2 = [%0], 1;;\n"
        "cmp4.lt p7,p0 = r2, r0\n"
        "(p7) br.cond.spnt.few 1b\n"
        : : "r"(lock), "r"(flags), "i"(IA64_PSR_I_BIT)
        : "p6", "p7", "r2", "memory");
}

#define arch_read_lock(lock) arch_read_lock_flags(lock, 0)

#else /* !ASM_SUPPORTED */

#define arch_read_lock_flags(rw, flags) arch_read_lock(rw)

#define arch_read_lock(rw)                              \
do {                                            \
    arch_rwlock_t *__read_lock_ptr = (rw);                      \
                                            \
    while (unlikely(ia64_fetchadd(1, (int *) __read_lock_ptr, acq) < 0)) {      \
        ia64_fetchadd(-1, (int *) __read_lock_ptr, rel);            \
        while (*(volatile int *)__read_lock_ptr < 0)                \
            cpu_relax();                            \
    }                                       \
} while (0)

#endif /* !ASM_SUPPORTED */

#define arch_read_unlock(rw)                    \
do {                                \
    arch_rwlock_t *__read_lock_ptr = (rw);          \
    ia64_fetchadd(-1, (int *) __read_lock_ptr, rel);    \
} while (0)

#ifdef ASM_SUPPORTED

static __always_inline void
arch_write_lock_flags(arch_rwlock_t *lock, unsigned long flags)
{
    __asm__ __volatile__ (
        "tbit.nz p6, p0 = %1, %2\n"
        "mov ar.ccv = r0\n"
        "dep r29 = -1, r0, 31, 1\n"
        "br.few 3f;;\n"
        "1:\n"
        "(p6) ssm psr.i\n"
        "2:\n"
        "hint @pause\n"
        "ld4 r2 = [%0];;\n"
        "cmp4.eq p0,p7 = r0, r2\n"
        "(p7) br.cond.spnt.few 2b\n"
        "(p6) rsm psr.i\n"
        ";;\n"
        "3:\n"
        "cmpxchg4.acq r2 = [%0], r29, ar.ccv;;\n"
        "cmp4.eq p0,p7 = r0, r2\n"
        "(p7) br.cond.spnt.few 1b;;\n"
        : : "r"(lock), "r"(flags), "i"(IA64_PSR_I_BIT)
        : "ar.ccv", "p6", "p7", "r2", "r29", "memory");
}

#define arch_write_lock(rw) arch_write_lock_flags(rw, 0)

#define arch_write_trylock(rw)                          \
({                                      \
    register long result;                           \
                                        \
    __asm__ __volatile__ (                          \
        "mov ar.ccv = r0\n"                     \
        "dep r29 = -1, r0, 31, 1;;\n"                   \
        "cmpxchg4.acq %0 = [%1], r29, ar.ccv\n"             \
        : "=r"(result) : "r"(rw) : "ar.ccv", "r29", "memory");      \
    (result == 0);                              \
})

static inline void arch_write_unlock(arch_rwlock_t *x)
{
    u8 *y = (u8 *)x;
    barrier();
    asm volatile ("st1.rel.nta [%0] = r0\n\t" :: "r"(y+3) : "memory" );
}

#else /* !ASM_SUPPORTED */

#define arch_write_lock_flags(l, flags) arch_write_lock(l)

#define arch_write_lock(l)                              \
({                                          \
    __u64 ia64_val, ia64_set_val = ia64_dep_mi(-1, 0, 31, 1);           \
    __u32 *ia64_write_lock_ptr = (__u32 *) (l);                 \
    do {                                        \
        while (*ia64_write_lock_ptr)                        \
            ia64_barrier();                         \
        ia64_val = ia64_cmpxchg4_acq(ia64_write_lock_ptr, ia64_set_val, 0); \
    } while (ia64_val);                             \
})

#define arch_write_trylock(rw)                      \
({                                  \
    __u64 ia64_val;                         \
    __u64 ia64_set_val = ia64_dep_mi(-1, 0, 31,1);          \
    ia64_val = ia64_cmpxchg4_acq((__u32 *)(rw), ia64_set_val, 0);   \
    (ia64_val == 0);                        \
})

static inline void arch_write_unlock(arch_rwlock_t *x)
{
    barrier();
    x->write_lock = 0;
}

#endif /* !ASM_SUPPORTED */

static inline int arch_read_trylock(arch_rwlock_t *x)
{
    union {
        arch_rwlock_t lock;
        __u32 word;
    } old, new;
    old.lock = new.lock = *x;
    old.lock.write_lock = new.lock.write_lock = 0;
    ++new.lock.read_counter;
    return (u32)ia64_cmpxchg4_acq((__u32 *)(x), new.word, old.word) == old.word;
}

#define arch_spin_relax(lock)   cpu_relax()
#define arch_read_relax(lock)   cpu_relax()
#define arch_write_relax(lock)  cpu_relax()

#endif /*  _ASM_IA64_SPINLOCK_H */