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/*
 * Copyright (C) 2001-2004 Jakub Jermar
 * 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.
 */


/** @addtogroup genericproc
 * @{
 */


/**
 * @file
 * @brief   Task management.
 */


#include <main/uinit.h>
#include <proc/thread.h>
#include <proc/task.h>
#include <proc/uarg.h>
#include <mm/as.h>
#include <mm/slab.h>
#include <synch/spinlock.h>
#include <arch.h>
#include <panic.h>
#include <adt/btree.h>
#include <adt/list.h>
#include <ipc/ipc.h>
#include <security/cap.h>
#include <memstr.h>
#include <print.h>
#include <elf.h>
#include <errno.h>
#include <syscall/copy.h>
#include <console/klog.h>

#ifndef LOADED_PROG_STACK_PAGES_NO
#define LOADED_PROG_STACK_PAGES_NO 1
#endif

/** Spinlock protecting the tasks_btree B+tree. */
SPINLOCK_INITIALIZE(tasks_lock);

/** B+tree of active tasks.
 *
 * The task is guaranteed to exist after it was found in the tasks_btree as long as:
 * @li the tasks_lock is held,
 * @li the task's lock is held when task's lock is acquired before releasing tasks_lock or
 * @li the task's refcount is grater than 0
 *
 */

btree_t tasks_btree;

static task_id_t task_counter = 0;

static void ktaskclnp(void *arg);
static void ktaskgc(void *arg);

/** Initialize tasks
 *
 * Initialize kernel tasks support.
 *
 */

void task_init(void)
{
    TASK = NULL;
    btree_create(&tasks_btree);
}


/** Create new task
 *
 * Create new task with no threads.
 *
 * @param as Task's address space.
 * @param name Symbolic name.
 *
 * @return New task's structure
 *
 */

task_t *task_create(as_t *as, char *name)
{
    ipl_t ipl;
    task_t *ta;
    int i;
   
    ta = (task_t *) malloc(sizeof(task_t), 0);

    task_create_arch(ta);

    spinlock_initialize(&ta->lock, "task_ta_lock");
    list_initialize(&ta->th_head);
    ta->as = as;
    ta->name = name;
    ta->main_thread = NULL;
    ta->refcount = 0;

    ta->capabilities = 0;
    ta->accept_new_threads = true;
   
    ipc_answerbox_init(&ta->answerbox);
    for (i=0; i < IPC_MAX_PHONES;i++)
        ipc_phone_init(&ta->phones[i]);
    if (ipc_phone_0)
        ipc_phone_connect(&ta->phones[0], ipc_phone_0);
    atomic_set(&ta->active_calls, 0);

    mutex_initialize(&ta->futexes_lock);
    btree_create(&ta->futexes);
   
    ipl = interrupts_disable();

    /*
     * Increment address space reference count.
     * TODO: Reconsider the locking scheme.
     */

    mutex_lock(&as->lock);
    as->refcount++;
    mutex_unlock(&as->lock);

    spinlock_lock(&tasks_lock);

    ta->taskid = ++task_counter;
    btree_insert(&tasks_btree, (btree_key_t) ta->taskid, (void *) ta, NULL);

    spinlock_unlock(&tasks_lock);
    interrupts_restore(ipl);

    return ta;
}

/** Destroy task.
 *
 * @param t Task to be destroyed.
 */

void task_destroy(task_t *t)
{
    task_destroy_arch(t);
    btree_destroy(&t->futexes);

    mutex_lock_active(&t->as->lock);
    if (--t->as->refcount == 0) {
        mutex_unlock(&t->as->lock);
        as_destroy(t->as);
        /*
         * t->as is destroyed.
         */

    } else {
        mutex_unlock(&t->as->lock);
    }
   
    free(t);
    TASK = NULL;
}

/** Create new task with 1 thread and run it
 *
 * @param program_addr Address of program executable image.
 * @param name Program name.
 *
 * @return Task of the running program or NULL on error.
 */

task_t * task_run_program(void *program_addr, char *name)
{
    as_t *as;
    as_area_t *a;
    int rc;
    thread_t *t1, *t2;
    task_t *task;
    uspace_arg_t *kernel_uarg;

    as = as_create(0);
    ASSERT(as);

    rc = elf_load((elf_header_t *) program_addr, as);
    if (rc != EE_OK) {
        as_destroy(as);
        return NULL;
    }
   
    kernel_uarg = (uspace_arg_t *) malloc(sizeof(uspace_arg_t), 0);
    kernel_uarg->uspace_entry = (void *) ((elf_header_t *) program_addr)->e_entry;
    kernel_uarg->uspace_stack = (void *) USTACK_ADDRESS;
    kernel_uarg->uspace_thread_function = NULL;
    kernel_uarg->uspace_thread_arg = NULL;
    kernel_uarg->uspace_uarg = NULL;
   
    task = task_create(as, name);
    ASSERT(task);

    /*
     * Create the data as_area.
     */

    a = as_area_create(as, AS_AREA_READ | AS_AREA_WRITE | AS_AREA_CACHEABLE,
        LOADED_PROG_STACK_PAGES_NO*PAGE_SIZE,
        USTACK_ADDRESS, AS_AREA_ATTR_NONE, &anon_backend, NULL);

    /*
     * Create the main thread.
     */

    t1 = thread_create(uinit, kernel_uarg, task, 0, "uinit");
    ASSERT(t1);
   
    /*
     * Create killer thread for the new task.
     */

    t2 = thread_create(ktaskgc, t1, task, 0, "ktaskgc");
    ASSERT(t2);
    thread_ready(t2);

    thread_ready(t1);

    return task;
}

/** Syscall for reading task ID from userspace.
 *
 * @param uspace_task_id Userspace address of 8-byte buffer where to store current task ID.
 *
 * @return 0 on success or an error code from @ref errno.h.
 */

__native sys_task_get_id(task_id_t *uspace_task_id)
{
    /*
     * No need to acquire lock on TASK because taskid
     * remains constant for the lifespan of the task.
     */

    return (__native) copy_to_uspace(uspace_task_id, &TASK->taskid, sizeof(TASK->taskid));
}

/** Find task structure corresponding to task ID.
 *
 * The tasks_lock must be already held by the caller of this function
 * and interrupts must be disabled.
 *
 * @param id Task ID.
 *
 * @return Task structure address or NULL if there is no such task ID.
 */

task_t *task_find_by_id(task_id_t id)
{
    btree_node_t *leaf;
   
    return (task_t *) btree_search(&tasks_btree, (btree_key_t) id, &leaf);
}

/** Kill task.
 *
 * @param id ID of the task to be killed.
 *
 * @return 0 on success or an error code from errno.h
 */

int task_kill(task_id_t id)
{
    ipl_t ipl;
    task_t *ta;
    thread_t *t;
    link_t *cur;

    if (id == 1)
        return EPERM;
   
    ipl = interrupts_disable();
    spinlock_lock(&tasks_lock);

    if (!(ta = task_find_by_id(id))) {
        spinlock_unlock(&tasks_lock);
        interrupts_restore(ipl);
        return ENOENT;
    }

    spinlock_lock(&ta->lock);
    ta->refcount++;
    spinlock_unlock(&ta->lock);

    btree_remove(&tasks_btree, ta->taskid, NULL);
    spinlock_unlock(&tasks_lock);
   
    t = thread_create(ktaskclnp, NULL, ta, 0, "ktaskclnp");
   
    spinlock_lock(&ta->lock);
    ta->accept_new_threads = false;
    ta->refcount--;

    /*
     * Interrupt all threads except ktaskclnp.
     */

    for (cur = ta->th_head.next; cur != &ta->th_head; cur = cur->next) {
        thread_t *thr;
        bool  sleeping = false;
       
        thr = list_get_instance(cur, thread_t, th_link);
        if (thr == t)
            continue;
           
        spinlock_lock(&thr->lock);
        thr->interrupted = true;
        if (thr->state == Sleeping)
            sleeping = true;
        spinlock_unlock(&thr->lock);
       
        if (sleeping)
            waitq_interrupt_sleep(thr);
    }
   
    spinlock_unlock(&ta->lock);
    interrupts_restore(ipl);
   
    if (t)
        thread_ready(t);

    return 0;
}

/** Print task list */
void task_print_list(void)
{
    link_t *cur;
    ipl_t ipl;
   
    /* Messing with thread structures, avoid deadlock */
    ipl = interrupts_disable();
    spinlock_lock(&tasks_lock);

    for (cur = tasks_btree.leaf_head.next; cur != &tasks_btree.leaf_head; cur = cur->next) {
        btree_node_t *node;
        int i;
       
        node = list_get_instance(cur, btree_node_t, leaf_link);
        for (i = 0; i < node->keys; i++) {
            task_t *t;
            int j;

            t = (task_t *) node->value[i];
       
            spinlock_lock(&t->lock);
            printf("%s(%lld): address=%#zx, as=%#zx, ActiveCalls: %zd",
                t->name, t->taskid, t, t->as, atomic_get(&t->active_calls));
            for (j=0; j < IPC_MAX_PHONES; j++) {
                if (t->phones[j].callee)
                    printf(" Ph(%zd): %#zx ", j, t->phones[j].callee);
            }
            printf("\n");
            spinlock_unlock(&t->lock);
        }
    }

    spinlock_unlock(&tasks_lock);
    interrupts_restore(ipl);
}

/** Kernel thread used to cleanup the task after it is killed. */
void ktaskclnp(void *arg)
{
    ipl_t ipl;
    thread_t *t = NULL, *main_thread;
    link_t *cur;
    bool again;

    thread_detach(THREAD);

loop:
    ipl = interrupts_disable();
    spinlock_lock(&TASK->lock);
   
    main_thread = TASK->main_thread;
   
    /*
     * Find a thread to join.
     */

    again = false;
    for (cur = TASK->th_head.next; cur != &TASK->th_head; cur = cur->next) {
        t = list_get_instance(cur, thread_t, th_link);

        spinlock_lock(&t->lock);
        if (t == THREAD) {
            spinlock_unlock(&t->lock);
            continue;
        } else if (t == main_thread) {
            spinlock_unlock(&t->lock);
            continue;
        } else if (t->join_type != None) {
            spinlock_unlock(&t->lock);
            again = true;
            continue;
        } else {
            t->join_type = TaskClnp;
            spinlock_unlock(&t->lock);
            again = false;
            break;
        }
    }
   
    spinlock_unlock(&TASK->lock);
    interrupts_restore(ipl);
   
    if (again) {
        /*
         * Other cleanup (e.g. ktaskgc) is in progress.
         */

        scheduler();
        goto loop;
    }
   
    if (t != THREAD) {
        ASSERT(t != main_thread);   /* uninit is joined and detached in ktaskgc */
        thread_join(t);
        thread_detach(t);
        goto loop;  /* go for another thread */
    }
   
    /*
     * Now there are no other threads in this task
     * and no new threads can be created.
     */

   
    ipc_cleanup();
    futex_cleanup();
    klog_printf("Cleanup of task %lld completed.", TASK->taskid);
}

/** Kernel thread used to kill the userspace task when its main thread exits.
 *
 * This thread waits until the main userspace thread (i.e. uninit) exits.
 * When this happens, the task is killed. In the meantime, exited threads
 * are garbage collected.
 *
 * @param arg Pointer to the thread structure of the task's main thread.
 */

void ktaskgc(void *arg)
{
    thread_t *t = (thread_t *) arg;
loop:  
    /*
     * Userspace threads cannot detach themselves,
     * therefore the thread pointer is guaranteed to be valid.
     */

    if (thread_join_timeout(t, 1000000, SYNCH_FLAGS_NONE) == ESYNCH_TIMEOUT) {  /* sleep uninterruptibly here! */
        ipl_t ipl;
        link_t *cur;
        thread_t *thr = NULL;
   
        /*
         * The join timed out. Try to do some garbage collection of Undead threads.
         */

more_gc:       
        ipl = interrupts_disable();
        spinlock_lock(&TASK->lock);
       
        for (cur = TASK->th_head.next; cur != &TASK->th_head; cur = cur->next) {
            thr = list_get_instance(cur, thread_t, th_link);
            spinlock_lock(&thr->lock);
            if (thr != t && thr->state == Undead && thr->join_type == None) {
                thr->join_type = TaskGC;
                spinlock_unlock(&thr->lock);
                break;
            }
            spinlock_unlock(&thr->lock);
            thr = NULL;
        }
        spinlock_unlock(&TASK->lock);
        interrupts_restore(ipl);
       
        if (thr) {
            thread_join(thr);
            thread_detach(thr);
            scheduler();
            goto more_gc;
        }
           
        goto loop;
    }
    thread_detach(t);
    task_kill(TASK->taskid);
}

/** @}
 */