source: mainline/uspace/srv/taskman/task.c@ d4ec49e

/*
 * copyright (c) 2009 martin decky
 * copyright (c) 2009 jiri svoboda
 * 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.
 */

/**
 * locking order:
 * - task_hash_table_lock,
 * - pending_wait_lock.
 *
 * @addtogroup taskman
 * @{
 */

#include <adt/hash_table.h>
#include <assert.h>
#include <async.h>
#include <errno.h>
#include <fibril_synch.h>
#include <macros.h>
#include <malloc.h>
#include <stdbool.h>
#include <stdio.h>
#include <task.h>
#include <types/task.h>

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

/** what type of retval from the task we have */
typedef enum {
        RVAL_UNSET,     /**< unset */
        RVAL_SET,       /**< retval set, e.g. by server */
        RVAL_SET_EXIT   /**< retval set, wait for expected task exit */
} retval_t;

/** task hash table item. */
typedef struct {
        ht_link_t link;
        
        task_id_t id;        /**< task id. */
        task_exit_t exit;    /**< task is done. */
        retval_t retval_type;  /**< task returned a value. */
        int retval;          /**< the return value. */
} hashed_task_t;


static size_t task_key_hash(void *key)
{
        return *(task_id_t*)key;
}

static size_t task_hash(const ht_link_t  *item)
{
        hashed_task_t *ht = hash_table_get_inst(item, hashed_task_t, link);
        return ht->id;
}

static bool task_key_equal(void *key, const ht_link_t *item)
{
        hashed_task_t *ht = hash_table_get_inst(item, hashed_task_t, link);
        return ht->id == *(task_id_t*)key;
}

/** perform actions after removal of item from the hash table. */
static void task_remove(ht_link_t *item)
{
        free(hash_table_get_inst(item, hashed_task_t, link));
}

/** operations for task hash table. */
static hash_table_ops_t task_hash_table_ops = {
        .hash = task_hash,
        .key_hash = task_key_hash,
        .key_equal = task_key_equal,
        .equal = NULL,
        .remove_callback = task_remove
};

/** Task hash table structure. */
static hash_table_t task_hash_table;
static FIBRIL_RWLOCK_INITIALIZE(task_hash_table_lock);

/** 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_callid_t callid;  /**< Call ID waiting for the connection */
        int flags;            /**< Wait flags */
} pending_wait_t;

static list_t pending_wait;
static FIBRIL_RWLOCK_INITIALIZE(pending_wait_lock);

int task_init(void)
{
        if (!hash_table_create(&task_hash_table, 0, 0, &task_hash_table_ops)) {
                printf(NAME ": No memory available for tasks\n");
                return ENOMEM;
        }
        
        list_initialize(&pending_wait);
        return EOK;
}

/** Process pending wait requests
 *
 * Assumes task_hash_table_lock is hold (at least read)
 */
void process_pending_wait(void)
{
        fibril_rwlock_write_lock(&pending_wait_lock);
loop:
        list_foreach(pending_wait, link, pending_wait_t, pr) {
                ht_link_t *link = hash_table_find(&task_hash_table, &pr->id);
                if (!link)
                        continue;
                
                hashed_task_t *ht = hash_table_get_inst(link, hashed_task_t, link);
                int notify_flags = 0;
                if (ht->exit != TASK_EXIT_RUNNING) {
                        notify_flags |= TASK_WAIT_EXIT;
                        if (ht->retval_type == RVAL_SET_EXIT) {
                                notify_flags |= TASK_WAIT_RETVAL;
                        }
                }
                if (ht->retval_type == RVAL_SET) {
                        notify_flags |= TASK_WAIT_RETVAL;
                }

                /*
                 * In current implementation you can wait for single retval,
                 * thus it can be never present in rest flags.
                 */
                int rest = (~notify_flags & pr->flags) & ~TASK_WAIT_RETVAL;
                rest &= ~TASK_WAIT_BOTH;
                int match = notify_flags & pr->flags;
                bool answer = !(pr->callid & IPC_CALLID_NOTIFICATION);
                printf("%s: %x; %x, %x\n", __func__, pr->flags, rest, match);

                if (match == 0) {
                        if (notify_flags & TASK_WAIT_EXIT) {
                                /* Nothing to wait for anymore */
                                if (answer) {
                                        async_answer_0(pr->callid, EINVAL);
                                }
                        } else {
                                /* Maybe later */
                                continue;
                        }
                } else if (answer) {
                        if ((pr->flags & TASK_WAIT_BOTH) && match == TASK_WAIT_EXIT) {
                                async_answer_1(pr->callid, EINVAL, ht->exit);
                        } else {
                                /* Send both exit status and retval, caller
                                 * should know what is valid */
                                async_answer_3(pr->callid, EOK, ht->exit,
                                    ht->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);
}

void wait_for_task(task_id_t id, int flags, ipc_callid_t callid, ipc_call_t *call)
{
        assert(!(flags & TASK_WAIT_BOTH) ||
            ((flags & TASK_WAIT_RETVAL) && (flags & TASK_WAIT_EXIT)));

        fibril_rwlock_read_lock(&task_hash_table_lock);
        ht_link_t *link = hash_table_find(&task_hash_table, &id);
        fibril_rwlock_read_unlock(&task_hash_table_lock);

        hashed_task_t *ht = (link != NULL) ?
            hash_table_get_inst(link, hashed_task_t, link) : NULL;
        
        if (ht == NULL) {
                /* No such task exists. */
                async_answer_0(callid, ENOENT);
                return;
        }
        
        if (ht->exit != TASK_EXIT_RUNNING) {
                //TODO are flags BOTH processed correctly here?
                async_answer_3(callid, EOK, ht->exit, ht->retval, 0);
                return;
        }
        
        /*
         * Add request to pending list or reuse existing item for a second
         * wait.
         */
        task_id_t waiter_id = call->in_task_id;
        fibril_rwlock_write_lock(&pending_wait_lock);
        pending_wait_t *pr = NULL;
        list_foreach(pending_wait, link, pending_wait_t, it) {
                if (it->id == id && it->waiter_id == waiter_id) {
                        pr = it;
                        break;
                }
        }

        int rc = EOK;
        bool reuse = false;
        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->callid = callid;

                list_append(&pr->link, &pending_wait);
                rc = EOK;
        } else if (!(pr->flags & TASK_WAIT_BOTH)) {
                /*
                 * One task can wait for another task only once (per task, not
                 * fibril).
                 */
                rc = EEXISTS;
        } else {
                /*
                 * Reuse pending wait for the second time.
                 */
                pr->flags &= ~TASK_WAIT_BOTH; // TODO maybe new flags should be set?
                pr->callid = callid;
                reuse = true;
        }
        printf("%s: %llu: %x, %x, %i\n", __func__, pr->id, flags, pr->flags, reuse);

finish:
        fibril_rwlock_write_unlock(&pending_wait_lock);
        // TODO why IPC_CALLID_NOTIFICATION? explain!
        if (rc != EOK && !(callid & IPC_CALLID_NOTIFICATION))
                async_answer_0(callid, rc);

}

int task_intro(ipc_call_t *call, bool check_unique)
{
        int rc = EOK;

        fibril_rwlock_write_lock(&task_hash_table_lock);

        ht_link_t *link = hash_table_find(&task_hash_table, &call->in_task_id);
        if (link != NULL) {
                rc = EEXISTS;
                goto finish;
        }
        
        hashed_task_t *ht = (hashed_task_t *) malloc(sizeof(hashed_task_t));
        if (ht == NULL) {
                rc = ENOMEM;
                goto finish;
        }

        /*
         * Insert into the main table.
         */
        ht->id = call->in_task_id;
        ht->exit = TASK_EXIT_RUNNING;
        ht->retval_type = RVAL_UNSET;
        ht->retval = -1;

        hash_table_insert(&task_hash_table, &ht->link);
        printf("%s: %llu\n", __func__, ht->id);
        
finish:
        fibril_rwlock_write_unlock(&task_hash_table_lock);
        return rc;
}

int task_set_retval(ipc_call_t *call)
{
        int rc = EOK;
        task_id_t id = call->in_task_id;
        
        fibril_rwlock_write_lock(&task_hash_table_lock);
        ht_link_t *link = hash_table_find(&task_hash_table, &id);

        hashed_task_t *ht = (link != NULL) ?
            hash_table_get_inst(link, hashed_task_t, link) : NULL;
        
        if ((ht == NULL) || (ht->exit != TASK_EXIT_RUNNING)) {
                rc = EINVAL;
                goto finish;
        }
        
        ht->retval = IPC_GET_ARG1(*call);
        ht->retval_type = IPC_GET_ARG2(*call) ? RVAL_SET_EXIT : RVAL_SET;
        
        process_pending_wait();
        
finish:
        fibril_rwlock_write_unlock(&task_hash_table_lock);
        return rc;
}

void task_terminated(task_id_t id, task_exit_t texit)
{
        /* Mark task as finished. */
        fibril_rwlock_write_lock(&task_hash_table_lock);
        ht_link_t *link = hash_table_find(&task_hash_table, &id);
        if (link == NULL) {
                goto finish;
        }

        hashed_task_t *ht = hash_table_get_inst(link, hashed_task_t, link);
        
        /*
         * If daemon returns a value and then fails/is killed, it's unexpected
         * termination.
         */
        if (ht->retval_type == RVAL_UNSET || texit == TASK_EXIT_UNEXPECTED) {
                ht->exit = TASK_EXIT_UNEXPECTED;
        } else {
                ht->exit = texit;
        }
        process_pending_wait();

        hash_table_remove_item(&task_hash_table, &ht->link);
finish:
        fibril_rwlock_write_unlock(&task_hash_table_lock);
}

/**
 * @}
 */