/*
 * Copyright (c) 2019 François Tigeot <ftigeot@wolfpond.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice unmodified, this list of conditions, and the following
 *    disclaimer.
 * 2. 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.
 *
 * 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.
 */

#include <linux/kthread.h>
#include <linux/sched.h>
#include <linux/slab.h>

#include <sys/kthread.h>

/*
   All Linux threads/processes have an associated task_struct
   a kthread is a pure kernel thread without userland context
*/

static void
linux_ktfn_wrapper(void *arg)
{
        struct task_struct *task = arg;

        task->kt_exitvalue = task->kt_fn(task->kt_fndata);
}

struct task_struct *
kthread_run(int (*lfn)(void *), void *data, const char *namefmt, ...)
{
        struct task_struct *task;
        struct thread *td;
        __va_list args;
        int ret;

        task = kzalloc(sizeof(*task), GFP_KERNEL);

        __va_start(args, namefmt);
        ret = kthread_alloc(linux_ktfn_wrapper, task, &td, namefmt, args);
        __va_end(args);
        if (ret) {
                kfree(task);
                return ERR_PTR(-ENOMEM);
        }

        task->dfly_td = td;
        td->td_linux_task = task;

        task->mm = NULL;        /* kthreads have no userland address space */

        task->kt_fn = lfn;
        task->kt_fndata = data;
        spin_init(&task->kt_spin, "tspin1");

        /* Start the thread here */
        lwkt_schedule(td);

        return task;
}

#define KTHREAD_SHOULD_STOP 1
#define KTHREAD_SHOULD_PARK 2

bool
kthread_should_stop(void)
{
        return test_bit(KTHREAD_SHOULD_STOP, &current->kt_flags);
}

int
kthread_stop(struct task_struct *ts)
{
        set_bit(KTHREAD_SHOULD_STOP, &ts->kt_flags);

        kthread_unpark(ts);
        wake_up_process(ts);

        /* XXX use a better mechanism to wait for the thread to finish running */
        tsleep(kthread_stop, 0, "kstop", hz);
        lwkt_free_thread(ts->dfly_td);

        return ts->kt_exitvalue;
}

int
kthread_park(struct task_struct *ts)
{
        set_bit(KTHREAD_SHOULD_PARK, &ts->kt_flags);
        wake_up_process(ts);

        return ts->kt_exitvalue;
}

void
kthread_unpark(struct task_struct *ts)
{
        clear_bit(KTHREAD_SHOULD_PARK, &ts->kt_flags);
        lwkt_schedule(ts->dfly_td);
        wake_up_process(ts);
}

bool
kthread_should_park(void)
{
        return test_bit(KTHREAD_SHOULD_PARK, &current->kt_flags);
}

void
kthread_parkme(void)
{
        if (test_bit(KTHREAD_SHOULD_PARK, &current->kt_flags) == 0)
                return;

        lwkt_deschedule_self(curthread);
}