source: mainline/kernel/generic/src/proc/task.c@ b3f8fb7

/*
 * 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 <lib/elf.h>
#include <errno.h>
#include <func.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 greater 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->context = CONTEXT;

        ta->capabilities = 0;
        ta->accept_new_threads = true;
        ta->cycles = 0;
        
        ipc_answerbox_init(&ta->answerbox);
        for (i = 0; i < IPC_MAX_PHONES; i++)
                ipc_phone_init(&ta->phones[i]);
        if ((ipc_phone_0) && (context_check(ipc_phone_0->task->context,
            ta->context)))
                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, THREAD_FLAG_USPACE,
            "uinit", false);
        ASSERT(t1);
        
        /*
         * Create killer thread for the new task.
         */
        t2 = thread_create(ktaskgc, t1, task, 0, "ktaskgc", true);
        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.
 */
unative_t 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 (unative_t) 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);
}

/** Get accounting data of given task.
 *
 * Note that task lock of 't' must be already held and
 * interrupts must be already disabled.
 *
 * @param t Pointer to thread.
 *
 */
uint64_t task_get_accounting(task_t *t)
{
        /* Accumulated value of task */
        uint64_t ret = t->cycles;
        
        /* Current values of threads */
        link_t *cur;
        for (cur = t->th_head.next; cur != &t->th_head; cur = cur->next) {
                thread_t *thr = list_get_instance(cur, thread_t, th_link);
                
                spinlock_lock(&thr->lock);
                /* Process only counted threads */
                if (!thr->uncounted) {
                        if (thr == THREAD) {
                                /* Update accounting of current thread */
                                thread_update_accounting();
                        } 
                        ret += thr->cycles;
                }
                spinlock_unlock(&thr->lock);
        }
        
        return ret;
}

/** 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", true);
        
        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)
                        thread_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);
        
        printf("taskid name       ctx address    as         cycles     threads "
            "calls  callee\n");
        printf("------ ---------- --- ---------- ---------- ---------- ------- "            "------ ------>\n");

        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);
                        
                        uint64_t cycles;
                        char suffix;
                        order(task_get_accounting(t), &cycles, &suffix);
                        
                        printf("%-6lld %-10s %-3ld %#10zx %#10zx %9llu%c %7zd "
                            "%6zd", t->taskid, t->name, t->context, t, t->as,
                            cycles, suffix, t->refcount,
                            atomic_get(&t->active_calls));
                        for (j = 0; j < IPC_MAX_PHONES; j++) {
                                if (t->phones[j].callee)
                                        printf(" %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);
}

/** @}
 */