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/*
* Copyright (c) 2009 Martin Decky
* 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 ns
* @{
*/
#include <ipc/ipc.h>
#include <libadt/hash_table.h>
#include <bool.h>
#include <errno.h>
#include <assert.h>
#include <stdio.h>
#include <macros.h>
#include "task.h"
#include "ns.h"
#define TASK_HASH_TABLE_CHAINS 256
/* TODO:
*
* The current implementation of waiting on a task is not perfect. If somebody
* wants to wait on a task which has already finished before the NS asked
* the kernel to receive notifications, it would block indefinitively.
*
* A solution to this is to fail immediately on a task for which no creation
* notification was received yet. However, there is a danger of a race condition
* in this solution -- the caller has to make sure that it is not trying to wait
* before the NS has a change to receive the task creation notification. This
* can be assured by waiting for this event in task_spawn().
*
* Finally, as there is currently no convention that each task has to be waited
* for, the NS can leak memory because of the zombie tasks.
*
*/
/** Task hash table item. */
typedef struct {
link_t link;
task_id_t id; /**< Task ID. */
bool destroyed;
} hashed_task_t;
/** Compute hash index into task hash table.
*
* @param key Pointer keys. However, only the first key (i.e. truncated task
* number) is used to compute the hash index.
*
* @return Hash index corresponding to key[0].
*
*/
static hash_index_t task_hash(unsigned long *key)
{
assert(key);
return (LOWER32(*key) % TASK_HASH_TABLE_CHAINS);
}
/** Compare a key with hashed item.
*
* @param key Array of keys.
* @param keys Must be lesser or equal to 2.
* @param item Pointer to a hash table item.
*
* @return Non-zero if the key matches the item, zero otherwise.
*
*/
static int task_compare(unsigned long key[], hash_count_t keys, link_t *item)
{
assert(key);
assert(keys <= 2);
assert(item);
hashed_task_t *ht = hash_table_get_instance(item, hashed_task_t, link);
if (keys == 2)
return ((LOWER32(key[1]) == UPPER32(ht->id))
&& (LOWER32(key[0]) == LOWER32(ht->id)));
else
return (LOWER32(key[0]) == LOWER32(ht->id));
}
/** Perform actions after removal of item from the hash table.
*
* @param item Item that was removed from the hash table.
*
*/
static void task_remove(link_t *item)
{
assert(item);
free(hash_table_get_instance(item, hashed_task_t, link));
}
/** Operations for task hash table. */
static hash_table_operations_t task_hash_table_ops = {
.hash = task_hash,
.compare = task_compare,
.remove_callback = task_remove
};
/** Task hash table structure. */
static hash_table_t task_hash_table;
/** Pending task wait structure. */
typedef struct {
link_t link;
task_id_t id; /**< Task ID. */
ipc_callid_t callid; /**< Call ID waiting for the connection */
} pending_wait_t;
static link_t pending_wait;
int task_init(void)
{
if (!hash_table_create(&task_hash_table, TASK_HASH_TABLE_CHAINS,
2, &task_hash_table_ops)) {
printf(NAME ": No memory available for tasks\n");
return ENOMEM;
}
if (event_subscribe(EVENT_WAIT, 0) != EOK)
printf(NAME ": Error registering wait notifications\n");
list_initialize(&pending_wait);
return EOK;
}
/** Process pending wait requests */
void process_pending_wait(void)
{
link_t *cur;
loop:
for (cur = pending_wait.next; cur != &pending_wait; cur = cur->next) {
pending_wait_t *pr = list_get_instance(cur, pending_wait_t, link);
unsigned long keys[2] = {
LOWER32(pr->id),
UPPER32(pr->id)
};
link_t *link = hash_table_find(&task_hash_table, keys);
if (!link)
continue;
hashed_task_t *ht = hash_table_get_instance(link, hashed_task_t, link);
if (!ht->destroyed)
continue;
if (!(pr->callid & IPC_CALLID_NOTIFICATION))
ipc_answer_0(pr->callid, EOK);
hash_table_remove(&task_hash_table, keys, 2);
list_remove(cur);
free(pr);
goto loop;
}
}
static void fail_pending_wait(task_id_t id, int rc)
{
link_t *cur;
loop:
for (cur = pending_wait.next; cur != &pending_wait; cur = cur->next) {
pending_wait_t *pr = list_get_instance(cur, pending_wait_t, link);
if (pr->id == id) {
if (!(pr->callid & IPC_CALLID_NOTIFICATION))
ipc_answer_0(pr->callid, rc);
list_remove(cur);
free(pr);
goto loop;
}
}
}
void wait_notification(wait_type_t et, task_id_t id)
{
unsigned long keys[2] = {
LOWER32(id),
UPPER32(id)
};
link_t *link = hash_table_find(&task_hash_table, keys);
if (link == NULL) {
hashed_task_t *ht =
(hashed_task_t *) malloc(sizeof(hashed_task_t));
if (ht == NULL) {
fail_pending_wait(id, ENOMEM);
return;
}
link_initialize(&ht->link);
ht->id = id;
ht->destroyed = (et == TASK_CREATE) ? false : true;
hash_table_insert(&task_hash_table, keys, &ht->link);
} else {
hashed_task_t *ht =
hash_table_get_instance(link, hashed_task_t, link);
ht->destroyed = (et == TASK_CREATE) ? false : true;
}
}
void wait_for_task(task_id_t id, ipc_call_t *call, ipc_callid_t callid)
{
ipcarg_t retval;
unsigned long keys[2] = {
LOWER32(id),
UPPER32(id)
};
link_t *link = hash_table_find(&task_hash_table, keys);
hashed_task_t *ht = (link != NULL) ?
hash_table_get_instance(link, hashed_task_t, link) : NULL;
if ((ht == NULL) || (!ht->destroyed)) {
/* Add to pending list */
pending_wait_t *pr =
(pending_wait_t *) malloc(sizeof(pending_wait_t));
if (!pr) {
retval = ENOMEM;
goto out;
}
pr->id = id;
pr->callid = callid;
list_append(&pr->link, &pending_wait);
return;
}
hash_table_remove(&task_hash_table, keys, 2);
retval = EOK;
out:
if (!(callid & IPC_CALLID_NOTIFICATION))
ipc_answer_0(callid, retval);
}
/**
* @}
*/