source: mainline/libc/generic/psthread.c@ 6c46350

/*
 * Copyright (C) 2006 Ondrej Palkovsky
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - 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.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * 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 <libadt/list.h>
#include <psthread.h>
#include <malloc.h>
#include <unistd.h>
#include <thread.h>
#include <stdio.h>
#include <kernel/arch/faddr.h>
#include <futex.h>
#include <assert.h>
#include <async.h>

#ifndef PSTHREAD_INITIAL_STACK_PAGES_NO
#define PSTHREAD_INITIAL_STACK_PAGES_NO 1
#endif

static LIST_INITIALIZE(ready_list);
static LIST_INITIALIZE(manager_list);

static void psthread_exit(void) __attribute__ ((noinline));
static void psthread_main(void);

static atomic_t psthread_futex = FUTEX_INITIALIZER;

/** Setup PSthread information into TCB structure */
psthread_data_t * psthread_setup()
{
        psthread_data_t *pt;
        tcb_t *tcb;

        tcb = __make_tls();
        if (!tcb)
                return NULL;

        pt = malloc(sizeof(*pt));
        if (!pt) {
                __free_tls(tcb);
                return NULL;
        }

        tcb->pst_data = pt;
        pt->tcb = tcb;

        return pt;
}

void psthread_teardown(psthread_data_t *pt)
{
        __free_tls(pt->tcb);
        free(pt);
}

/** Function to preempt to other pseudo thread without adding
 * currently running pseudo thread to ready_list.
 */
void psthread_exit(void)
{
        psthread_data_t *pt;

        futex_down(&psthread_futex);

        if (!list_empty(&ready_list))
                pt = list_get_instance(ready_list.next, psthread_data_t, link);
        else if (!list_empty(&manager_list)) 
                pt = list_get_instance(manager_list.next, psthread_data_t, link);
        else {
                printf("Cannot find suitable psthread to run.\n");
                _exit(0);
        }
        list_remove(&pt->link);
        futex_up(&psthread_futex);

        context_restore(&pt->ctx);
        /* Never reached */
}

/** Function that is called on entry to new uspace thread */
void psthread_main(void)
{
        psthread_data_t *pt = __tcb_get()->pst_data;

        pt->retval = pt->func(pt->arg);

        pt->finished = 1;
        if (pt->waiter)
                list_append(&pt->waiter->link, &ready_list);

        psthread_exit();
}

/** Schedule next userspace pseudo thread.
 *
 * If calling with PS_TO_MANAGER parameter, the async_futex should be
 * held.
 *
 * @param tomanager If true, we are switching to next ready manager thread
 *                  (if none is found, thread is exited)
 * @param frommanager If true, we are switching from manager thread
 * @return 0 if there is no ready pseudo thread, 1 otherwise.
 */
int psthread_schedule_next_adv(pschange_type ctype)
{
        psthread_data_t *pt;
        int retval = 0;
        
        futex_down(&psthread_futex);

        if (ctype == PS_PREEMPT && list_empty(&ready_list))
                goto ret_0;

        if (ctype == PS_FROM_MANAGER && list_empty(&ready_list)) {
                goto ret_0;
        }
        /* If we are going to manager and none exists, create it */
        while (ctype == PS_TO_MANAGER && list_empty(&manager_list)) {
                futex_up(&psthread_futex);
                async_create_manager();
                futex_down(&psthread_futex);
        }

        pt = __tcb_get()->pst_data;
        if (!context_save(&pt->ctx)) 
                return 1; // futex_up already done here

        if (ctype == PS_PREEMPT)
                list_append(&pt->link, &ready_list);
        else if (ctype == PS_FROM_MANAGER)
                list_append(&pt->link, &manager_list);
        
        if (ctype == PS_TO_MANAGER)
                pt = list_get_instance(manager_list.next,psthread_data_t, link);
        else
                pt = list_get_instance(ready_list.next, psthread_data_t, link);
        list_remove(&pt->link);

        futex_up(&psthread_futex);
        context_restore(&pt->ctx);

ret_0:
        futex_up(&psthread_futex);
        return retval;
}

/** Wait for uspace pseudo thread to finish.
 *
 * @param psthrid Pseudo thread to wait for.
 *
 * @return Value returned by the finished thread.
 */
int psthread_join(pstid_t psthrid)
{
        volatile psthread_data_t *pt, *mypt;
        volatile int retval;

        /* Handle psthrid = Kernel address -> it is wait for call */
        pt = (psthread_data_t *) psthrid;

        if (!pt->finished) {
                mypt = __tcb_get()->pst_data;
                if (context_save(&((psthread_data_t *) mypt)->ctx)) {
                        pt->waiter = (psthread_data_t *) mypt;
                        psthread_exit();
                }
        }
        retval = pt->retval;

        free(pt->stack);
        psthread_teardown((void *)pt);

        return retval;
}

/**
 * Create a userspace thread
 *
 * @param func Pseudo thread function.
 * @param arg Argument to pass to func.
 *
 * @return 0 on failure, TLS of the new pseudo thread.
 */
pstid_t psthread_create(int (*func)(void *), void *arg)
{
        psthread_data_t *pt;

        pt = psthread_setup();
        if (!pt) 
                return 0;
        pt->stack = (char *) malloc(PSTHREAD_INITIAL_STACK_PAGES_NO*getpagesize());

        if (!pt->stack) {
                psthread_teardown(pt);
                return 0;
        }

        pt->arg= arg;
        pt->func = func;
        pt->finished = 0;
        pt->waiter = NULL;

        context_save(&pt->ctx);
        context_set(&pt->ctx, FADDR(psthread_main), pt->stack, PSTHREAD_INITIAL_STACK_PAGES_NO*getpagesize(),
                    pt->tcb);

        return (pstid_t )pt;
}

/** Add a thread to ready list */
void psthread_add_ready(pstid_t psthrid)
{
        psthread_data_t *pt;

        pt = (psthread_data_t *) psthrid;
        futex_down(&psthread_futex);
        list_append(&pt->link, &ready_list);
        futex_up(&psthread_futex);
}

/** Add a thread to manager list */
void psthread_add_manager(pstid_t psthrid)
{
        psthread_data_t *pt;

        pt = (psthread_data_t *) psthrid;

        futex_down(&psthread_futex);
        list_append(&pt->link, &manager_list);
        futex_up(&psthread_futex);
}

/** Remove one manager from manager list */
void psthread_remove_manager()
{
        futex_down(&psthread_futex);
        if (list_empty(&manager_list)) {
                futex_up(&psthread_futex);
                return;
        }
        list_remove(manager_list.next);
        futex_up(&psthread_futex);
}

/** Return thread id of current running thread */
pstid_t psthread_get_id(void)
{
        return (pstid_t)__tcb_get()->pst_data;
}