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/*

 * kernel/locking/mutex.c

 *

 * Mutexes: blocking mutual exclusion locks

 *

 * Started by Ingo Molnar:

 *

 *  Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar 

 *

 * Many thanks to Arjan van de Ven, Thomas Gleixner, Steven Rostedt and

 * David Howells for suggestions and improvements.

 *

 *  - Adaptive spinning for mutexes by Peter Zijlstra. (Ported to mainline

 *    from the -rt tree, where it was originally implemented for rtmutexes

 *    by Steven Rostedt, based on work by Gregory Haskins, Peter Morreale

 *    and Sven Dietrich.

 *

 * Also see Documentation/mutex-design.txt.

 */

#include 

#include 

#include 

#include 

#include 

#include 

#include 

static inline void mutex_set_owner(struct mutex *lock)

{

}

/*

 * A negative mutex count indicates that waiters are sleeping waiting for the

 * mutex.

 */

#define MUTEX_SHOW_NO_WAITER(mutex) (atomic_read(&(mutex)->count) >= 0)

void

__mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key)

{

    atomic_set(&lock->count, 1);

//    spin_lock_init(&lock->wait_lock);

    INIT_LIST_HEAD(&lock->wait_list);

//    mutex_clear_owner(lock);

#ifdef CONFIG_MUTEX_SPIN_ON_OWNER

    lock->osq = NULL;

#endif

}

static inline int __ww_mutex_lock_check_stamp(struct mutex *lock, struct ww_acquire_ctx *ctx)

{

        struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);

        struct ww_acquire_ctx *hold_ctx = READ_ONCE(ww->ctx);

        if (!hold_ctx)

                return 0;

        if (unlikely(ctx == hold_ctx))

                return -EALREADY;

        if (ctx->stamp - hold_ctx->stamp <= LONG_MAX &&

            (ctx->stamp != hold_ctx->stamp || ctx > hold_ctx)) {

                return -EDEADLK;

        }

        return 0;

}

static __always_inline void ww_mutex_lock_acquired(struct ww_mutex *ww,

                           struct ww_acquire_ctx *ww_ctx)

{

    ww_ctx->acquired++;

}

void ww_mutex_unlock(struct ww_mutex *lock)

{

    /*

     * The unlocking fastpath is the 0->1 transition from 'locked'

     * into 'unlocked' state:

     */

    if (lock->ctx) {

            if (lock->ctx->acquired > 0)

                    lock->ctx->acquired--;

            lock->ctx = NULL;

    }

    MutexUnlock(&lock->base);

}

static inline int __mutex_fastpath_lock_retval(atomic_t *count)

{

    if (unlikely(atomic_dec_return(count) < 0))

        return -1;

    else

        return 0;

}

static __always_inline void

ww_mutex_set_context_fastpath(struct ww_mutex *lock,

                               struct ww_acquire_ctx *ctx)

{

    u32 flags;

    struct mutex_waiter *cur;

    ww_mutex_lock_acquired(lock, ctx);

    lock->ctx = ctx;

    /*

     * The lock->ctx update should be visible on all cores before

     * the atomic read is done, otherwise contended waiters might be

     * missed. The contended waiters will either see ww_ctx == NULL

     * and keep spinning, or it will acquire wait_lock, add itself

     * to waiter list and sleep.

     */

    smp_mb(); /* ^^^ */

    /*

     * Check if lock is contended, if not there is nobody to wake up

     */

    if (likely(atomic_read(&lock->base.count) == 0))

            return;

    /*

     * Uh oh, we raced in fastpath, wake up everyone in this case,

     * so they can see the new lock->ctx.

     */

    flags = safe_cli();

    list_for_each_entry(cur, &lock->base.wait_list, list) {

        ((struct kos_appdata*)cur->task)->state = KOS_SLOT_STATE_RUNNING;

    }

    safe_sti(flags);

}

static __always_inline void

ww_mutex_set_context_slowpath(struct ww_mutex *lock,

                              struct ww_acquire_ctx *ctx)

{

    struct mutex_waiter *cur;

    ww_mutex_lock_acquired(lock, ctx);

    lock->ctx = ctx;

    /*

     * Give any possible sleeping processes the chance to wake up,

     * so they can recheck if they have to back off.

     */

    list_for_each_entry(cur, &lock->base.wait_list, list) {

        ((struct kos_appdata*)cur->task)->state = KOS_SLOT_STATE_RUNNING;

    }

}

int __ww_mutex_lock_slowpath(struct ww_mutex *ww, struct ww_acquire_ctx *ctx)

{

    struct mutex *lock;

    struct mutex_waiter waiter;

    struct kos_appdata *appdata;

    u32 eflags;

    int ret = 0;

    lock = &ww->base;

    appdata = GetCurrSlot();

    waiter.task = appdata;

    eflags = safe_cli();

    list_add_tail(&waiter.list, &lock->wait_list);

    for(;;)

    {

        if( atomic_xchg(&lock->count, -1) == 1)

            break;

        if (ctx->acquired > 0) {

            ret = __ww_mutex_lock_check_stamp(lock, ctx);

            if (ret)

                goto err;

        };

        appdata->state = KOS_SLOT_STATE_SUSPENDED;

        change_task();

    };

    if (likely(list_empty(&lock->wait_list)))

        atomic_set(&lock->count, 0);

    ww_mutex_set_context_slowpath(ww, ctx);

err:

    list_del(&waiter.list);

    safe_sti(eflags);

    return ret;

}

int __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)

{

    int ret;

    ret = __mutex_fastpath_lock_retval(&lock->base.count);

    if (likely(!ret)) {

            ww_mutex_set_context_fastpath(lock, ctx);

            mutex_set_owner(&lock->base);

    } else

            ret = __ww_mutex_lock_slowpath(lock, ctx);

    return ret;

}

int __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)

{

    int ret;

    ret = __mutex_fastpath_lock_retval(&lock->base.count);

    if (likely(!ret)) {

            ww_mutex_set_context_fastpath(lock, ctx);

            mutex_set_owner(&lock->base);

    } else

            ret = __ww_mutex_lock_slowpath(lock, ctx);

    return ret;

}