#ifndef _ASM_X86_SPINLOCK_H
#define _ASM_X86_SPINLOCK_H

#include <linux/jump_label.h>
#include <linux/atomic.h>
#include <asm/page.h>
#include <asm/processor.h>
#include <linux/compiler.h>
#include <asm/paravirt.h>
#include <asm/bitops.h>

/*
 * Your basic SMP spinlocks, allowing only a single CPU anywhere
 *
 * Simple spin lock operations.  There are two variants, one clears IRQ's
 * on the local processor, one does not.
 *
 * These are fair FIFO ticket locks, which support up to 2^16 CPUs.
 *
 * (the type definitions are in asm/spinlock_types.h)
 */

#ifdef CONFIG_X86_32
# define LOCK_PTR_REG "a"
#else
# define LOCK_PTR_REG "D"
#endif

#if defined(CONFIG_X86_32) && (defined(CONFIG_X86_PPRO_FENCE))
/*
 * On PPro SMP, we use a locked operation to unlock
 * (PPro errata 66, 92)
 */
# define UNLOCK_LOCK_PREFIX LOCK_PREFIX
#else
# define UNLOCK_LOCK_PREFIX
#endif

/* How long a lock should spin before we consider blocking */
#define SPIN_THRESHOLD  (1 << 15)

extern struct static_key paravirt_ticketlocks_enabled;
static __always_inline bool static_key_false(struct static_key *key);

#ifdef CONFIG_QUEUED_SPINLOCKS
#include <asm/qspinlock.h>
#else

#ifdef CONFIG_PARAVIRT_SPINLOCKS

static inline void __ticket_enter_slowpath(arch_spinlock_t *lock)
{
        set_bit(0, (volatile unsigned long *)&lock->tickets.head);
}

#else  /* !CONFIG_PARAVIRT_SPINLOCKS */
static __always_inline void __ticket_lock_spinning(arch_spinlock_t *lock,
                                                        __ticket_t ticket)
{
}
static inline void __ticket_unlock_kick(arch_spinlock_t *lock,
                                                        __ticket_t ticket)
{
}

#endif /* CONFIG_PARAVIRT_SPINLOCKS */
static inline int  __tickets_equal(__ticket_t one, __ticket_t two)
{
        return !((one ^ two) & ~TICKET_SLOWPATH_FLAG);
}

static inline void __ticket_check_and_clear_slowpath(arch_spinlock_t *lock,
                                                        __ticket_t head)
{
        if (head & TICKET_SLOWPATH_FLAG) {
                arch_spinlock_t old, new;

                old.tickets.head = head;
                new.tickets.head = head & ~TICKET_SLOWPATH_FLAG;
                old.tickets.tail = new.tickets.head + TICKET_LOCK_INC;
                new.tickets.tail = old.tickets.tail;

                /* try to clear slowpath flag when there are no contenders */
                cmpxchg(&lock->head_tail, old.head_tail, new.head_tail);
        }
}

static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
{
        return __tickets_equal(lock.tickets.head, lock.tickets.tail);
}

/*
 * 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.
 *
 * We use an xadd covering *both* parts of the lock, to increment the tail and
 * also load the position of the head, which takes care of memory ordering
 * issues and should be optimal for the uncontended case. Note the tail must be
 * in the high part, because a wide xadd increment of the low part would carry
 * up and contaminate the high part.
 */
static __always_inline void arch_spin_lock(arch_spinlock_t *lock)
{
        register struct __raw_tickets inc = { .tail = TICKET_LOCK_INC };

        inc = xadd(&lock->tickets, inc);
        if (likely(inc.head == inc.tail))
                goto out;

        for (;;) {
                unsigned count = SPIN_THRESHOLD;

                do {
                        inc.head = READ_ONCE(lock->tickets.head);
                        if (__tickets_equal(inc.head, inc.tail))
                                goto clear_slowpath;
                        cpu_relax();
                } while (--count);
                __ticket_lock_spinning(lock, inc.tail);
        }
clear_slowpath:
        __ticket_check_and_clear_slowpath(lock, inc.head);
out:
        barrier();      /* make sure nothing creeps before the lock is taken */
}

static __always_inline int arch_spin_trylock(arch_spinlock_t *lock)
{
        arch_spinlock_t old, new;

        old.tickets = READ_ONCE(lock->tickets);
        if (!__tickets_equal(old.tickets.head, old.tickets.tail))
                return 0;

        new.head_tail = old.head_tail + (TICKET_LOCK_INC << TICKET_SHIFT);
        new.head_tail &= ~TICKET_SLOWPATH_FLAG;

        /* cmpxchg is a full barrier, so nothing can move before it */
        return cmpxchg(&lock->head_tail, old.head_tail, new.head_tail) == old.head_tail;
}

static __always_inline void arch_spin_unlock(arch_spinlock_t *lock)
{
        if (TICKET_SLOWPATH_FLAG &&
                static_key_false(&paravirt_ticketlocks_enabled)) {
                __ticket_t head;

                BUILD_BUG_ON(((__ticket_t)NR_CPUS) != NR_CPUS);

                head = xadd(&lock->tickets.head, TICKET_LOCK_INC);

                if (unlikely(head & TICKET_SLOWPATH_FLAG)) {
                        head &= ~TICKET_SLOWPATH_FLAG;
                        __ticket_unlock_kick(lock, (head + TICKET_LOCK_INC));
                }
        } else
                __add(&lock->tickets.head, TICKET_LOCK_INC, UNLOCK_LOCK_PREFIX);
}

static inline int arch_spin_is_locked(arch_spinlock_t *lock)
{
        struct __raw_tickets tmp = READ_ONCE(lock->tickets);

        return !__tickets_equal(tmp.tail, tmp.head);
}

static inline int arch_spin_is_contended(arch_spinlock_t *lock)
{
        struct __raw_tickets tmp = READ_ONCE(lock->tickets);

        tmp.head &= ~TICKET_SLOWPATH_FLAG;
        return (__ticket_t)(tmp.tail - tmp.head) > TICKET_LOCK_INC;
}
#define arch_spin_is_contended  arch_spin_is_contended

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_t head = READ_ONCE(lock->tickets.head);

        for (;;) {
                struct __raw_tickets tmp = READ_ONCE(lock->tickets);
                /*
                 * We need to check "unlocked" in a loop, tmp.head == head
                 * can be false positive because of overflow.
                 */
                if (__tickets_equal(tmp.head, tmp.tail) ||
                                !__tickets_equal(tmp.head, head))
                        break;

                cpu_relax();
        }
}
#endif /* CONFIG_QUEUED_SPINLOCKS */

/*
 * Read-write spinlocks, allowing multiple readers
 * but only one writer.
 *
 * NOTE! it is quite common to have readers in interrupts
 * but no interrupt writers. For those circumstances we
 * can "mix" irq-safe locks - any writer needs to get a
 * irq-safe write-lock, but readers can get non-irqsafe
 * read-locks.
 *
 * On x86, we implement read-write locks using the generic qrwlock with
 * x86 specific optimization.
 */

#include <asm/qrwlock.h>

#define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
#define arch_write_lock_flags(lock, flags) arch_write_lock(lock)

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

#endif /* _ASM_X86_SPINLOCK_H */