source: mainline/uspace/srv/taskman/event.c@ 3529f148

/*
 * Copyright (c) 2015 Michal Koutny
 * 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 taskman
 * @{
 */

#include <adt/list.h>
#include <assert.h>
#include <errno.h>
#include <ipc/taskman.h>
#include <stdlib.h>
#include <task.h>

#include "event.h"
#include "task.h"
#include "taskman.h"

/** Pending task wait structure. */
typedef struct {
        link_t link;
        task_id_t id;         /**< Task ID who we wait for. */
        task_id_t waiter_id;  /**< Task ID who waits. */
        ipc_call_t *icall;  /**< Call ID waiting for the event. */
        task_wait_flag_t flags; /**< Wait flags. */
} pending_wait_t;

static list_t pending_waits;
static FIBRIL_RWLOCK_INITIALIZE(pending_wait_lock);

static list_t listeners;
static FIBRIL_RWLOCK_INITIALIZE(listeners_lock);

errno_t event_init(void)
{
        list_initialize(&pending_waits);
        list_initialize(&listeners);

        return EOK;
}

static task_wait_flag_t event_flags(task_t *task)
{
        task_wait_flag_t flags = TASK_WAIT_NONE;
        if (task->retval_type == RVAL_SET) {
                flags |= TASK_WAIT_RETVAL;
        }

        if (task->exit != TASK_EXIT_RUNNING) {
                flags |= TASK_WAIT_EXIT;
                if (task->retval_type == RVAL_SET_EXIT) {
                        flags |= TASK_WAIT_RETVAL;
                } else {
                        /* Don't notify retval of exited task */
                        flags &= ~TASK_WAIT_RETVAL;
                }
        }
        return flags;
}

static void event_notify(task_t *sender, async_sess_t *sess)
{
        task_wait_flag_t flags = event_flags(sender);
        if (flags == TASK_WAIT_NONE) {
                return;
        }

        async_exch_t *exch = async_exchange_begin(sess);
        aid_t req = async_send_5(exch, TASKMAN_EV_TASK,
            LOWER32(sender->id),
            UPPER32(sender->id),
            flags,
            sender->exit,
            sender->retval,
            NULL);

        async_exchange_end(exch);

        /* Just send a notification and don't wait for anything */
        async_forget(req);
}

/** Notify all registered listeners about sender's event
 *
 * @note Assumes share lock of task_hash_table is held.
 */
static void event_notify_all(task_t *sender)
{
        task_wait_flag_t flags = event_flags(sender);
        if (flags == TASK_WAIT_NONE) {
                return;
        }

        fibril_rwlock_read_lock(&listeners_lock);
        list_foreach(listeners, listeners, task_t, t) {
                assert(t->sess);
                event_notify(sender, t->sess);
        }
        fibril_rwlock_read_unlock(&listeners_lock);
}

/** Process pending wait requests
 *
 * Assumes task_hash_table_lock is hold (at least read)
 */
static void process_pending_wait(void)
{
        fibril_rwlock_write_lock(&pending_wait_lock);
loop:
        list_foreach(pending_waits, link, pending_wait_t, pr) {
                task_t *t = task_get_by_id(pr->id);
                if (t == NULL) {
                        continue; // TODO really when does this happen?
                }
                task_wait_flag_t notify_flags = event_flags(t);

                /*
                 * In current implementation you can wait for single retval,
                 * thus it can be never present in rest flags.
                 */
                task_wait_flag_t rest = (~notify_flags & pr->flags) & ~TASK_WAIT_RETVAL;
                rest &= ~TASK_WAIT_BOTH;
                bool match = notify_flags & pr->flags;
                // TODO why do I even accept such calls?
                bool answer = !(pr->icall->flags & IPC_CALL_NOTIF);

                if (match == 0) {
                        if (notify_flags & TASK_WAIT_EXIT) {
                                /* Nothing to wait for anymore */
                                if (answer) {
                                        async_answer_0(pr->icall, EINTR);
                                }
                        } else {
                                /* Maybe later */
                                continue;
                        }
                } else if (answer) {
                        if ((pr->flags & TASK_WAIT_BOTH) && match == TASK_WAIT_EXIT) {
                                /* No sense to wait for both anymore */
                                async_answer_1(pr->icall, EINTR, t->exit);
                        } else {
                                /*
                                 * Send both exit status and retval, caller
                                 * should know what is valid
                                 */
                                async_answer_3(pr->icall, EOK, t->exit,
                                    t->retval, rest);
                        }

                        /* Pending wait has one more chance  */
                        if (rest && (pr->flags & TASK_WAIT_BOTH)) {
                                pr->flags = rest | TASK_WAIT_BOTH;
                                continue;
                        }
                }

                list_remove(&pr->link);
                free(pr);
                goto loop;
        }
        fibril_rwlock_write_unlock(&pending_wait_lock);
}

static bool dump_walker(task_t *t, void *arg)
{
        event_notify(t, arg);
        return true;
}

void event_register_listener(task_id_t id, bool past_events, async_sess_t *sess,
    ipc_call_t *icall)
{
        errno_t rc = EOK;
        /*
         * We have lock of tasks structures so that we can guarantee
         * that dump receiver will receive tasks correctly ordered (retval,
         * exit updates are serialized via exclusive lock).
         */
        fibril_rwlock_write_lock(&task_hash_table_lock);
        fibril_rwlock_write_lock(&listeners_lock);

        task_t *t = task_get_by_id(id);
        if (t == NULL) {
                rc = ENOENT;
                goto finish;
        }
        assert(t->sess == NULL);
        list_append(&t->listeners, &listeners);
        t->sess = sess;

        /*
         * Answer caller first, so that they are not unnecessarily waiting
         * while we dump events.
         */
        async_answer_0(icall, rc);
        if (past_events) {
                task_foreach(&dump_walker, t->sess);
        }

finish:
        fibril_rwlock_write_unlock(&listeners_lock);
        fibril_rwlock_write_unlock(&task_hash_table_lock);
        if (rc != EOK) {
                async_answer_0(icall, rc);
        }
}

void wait_for_task(task_id_t id, task_wait_flag_t flags, ipc_call_t *icall,
    task_id_t waiter_id)
{
        assert(!(flags & TASK_WAIT_BOTH) ||
            ((flags & TASK_WAIT_RETVAL) && (flags & TASK_WAIT_EXIT)));

        fibril_rwlock_read_lock(&task_hash_table_lock);
        task_t *t = task_get_by_id(id);
        fibril_rwlock_read_unlock(&task_hash_table_lock);

        if (t == NULL) {
                /* No such task exists. */
                async_answer_0(icall, ENOENT);
                return;
        }

        if (t->exit != TASK_EXIT_RUNNING) {
                //TODO are flags BOTH processed correctly here?
                async_answer_3(icall, EOK, t->exit, t->retval, 0);
                return;
        }

        /*
         * Add request to pending list or reuse existing item for a second
         * wait.
         */
        fibril_rwlock_write_lock(&pending_wait_lock);
        pending_wait_t *pr = NULL;
        list_foreach(pending_waits, link, pending_wait_t, it) {
                if (it->id == id && it->waiter_id == waiter_id) {
                        pr = it;
                        break;
                }
        }

        errno_t rc = EOK;
        if (pr == NULL) {
                pr = malloc(sizeof(pending_wait_t));
                if (!pr) {
                        rc = ENOMEM;
                        goto finish;
                }

                link_initialize(&pr->link);
                pr->id = id;
                pr->waiter_id = waiter_id;
                pr->flags = flags;
                pr->icall = icall;

                list_append(&pr->link, &pending_waits);
                rc = EOK;
        } else if (!(pr->flags & TASK_WAIT_BOTH)) {
                /*
                 * One task can wait for another task only once (per task, not
                 * fibril).
                 */
                rc = EEXIST;
        } else {
                /*
                 * Reuse pending wait for the second time.
                 */
                pr->flags &= ~TASK_WAIT_BOTH; // TODO maybe new flags should be set?
                pr->icall = icall;
        }

finish:
        fibril_rwlock_write_unlock(&pending_wait_lock);
        // TODO why IPC_CALLID_NOTIFICATION? explain!
        if (rc != EOK && !(icall->flags & IPC_CALL_NOTIF)) {
                async_answer_0(icall, rc);
        }
}

errno_t task_set_retval(task_id_t sender, int retval, bool wait_for_exit)
{
        errno_t rc = EOK;

        fibril_rwlock_write_lock(&task_hash_table_lock);
        task_t *t = task_get_by_id(sender);

        if ((t == NULL) || (t->exit != TASK_EXIT_RUNNING)) {
                rc = EINVAL;
                goto finish;
        }

        t->retval = retval;
        t->retval_type = wait_for_exit ? RVAL_SET_EXIT : RVAL_SET;

        event_notify_all(t);
        process_pending_wait();

finish:
        fibril_rwlock_write_unlock(&task_hash_table_lock);
        return rc;
}

void task_terminated(task_id_t id, exit_reason_t exit_reason)
{
        /* Mark task as finished. */
        fibril_rwlock_write_lock(&task_hash_table_lock);
        task_t *t = task_get_by_id(id);
        if (t == NULL) {
                goto finish;
        }

        /*
         * If daemon returns a value and then fails/is killed, it's an
         * unexpected termination.
         */
        if (t->retval_type == RVAL_UNSET || exit_reason == EXIT_REASON_KILLED) {
                t->exit = TASK_EXIT_UNEXPECTED;
        } else if (t->failed) {
                t->exit = TASK_EXIT_UNEXPECTED;
        } else  {
                t->exit = TASK_EXIT_NORMAL;
        }

        /*
         * First remove terminated task from listeners and only after that
         * notify all others.
         */
        fibril_rwlock_write_lock(&listeners_lock);
        list_remove(&t->listeners);
        fibril_rwlock_write_unlock(&listeners_lock);

        event_notify_all(t);
        process_pending_wait();

        /* Eventually, get rid of task_t. */
        task_remove(&t);

finish:
        fibril_rwlock_write_unlock(&task_hash_table_lock);
}

void task_failed(task_id_t id)
{
        /* Mark task as failed. */
        fibril_rwlock_write_lock(&task_hash_table_lock);
        task_t *t = task_get_by_id(id);
        if (t == NULL) {
                goto finish;
        }

        t->failed = true;
        // TODO design substitution for taskmon (monitoring) = invoke dump
        // utility or pass event to registered tasks

finish:
        fibril_rwlock_write_unlock(&task_hash_table_lock);
}

/**
 * @}
 */