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  1. /*
  2.  * Copyright (c) 2009 Martin Decky
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. /** @addtogroup ns
  30.  * @{
  31.  */
  32.  
  33. #include <ipc/ipc.h>
  34. #include <libadt/hash_table.h>
  35. #include <bool.h>
  36. #include <errno.h>
  37. #include <assert.h>
  38. #include <stdio.h>
  39. #include <macros.h>
  40. #include "task.h"
  41. #include "ns.h"
  42.  
  43. #define TASK_HASH_TABLE_CHAINS  256
  44.  
  45. /* TODO:
  46.  *
  47.  * The current implementation of waiting on a task is not perfect. If somebody
  48.  * wants to wait on a task which has already finished before the NS asked
  49.  * the kernel to receive notifications, it would block indefinitively.
  50.  *
  51.  * A solution to this is to fail immediately on a task for which no creation
  52.  * notification was received yet. However, there is a danger of a race condition
  53.  * in this solution -- the caller has to make sure that it is not trying to wait
  54.  * before the NS has a change to receive the task creation notification. This
  55.  * can be assured by waiting for this event in task_spawn().
  56.  *
  57.  * Finally, as there is currently no convention that each task has to be waited
  58.  * for, the NS can leak memory because of the zombie tasks.
  59.  *
  60.  */
  61.  
  62. /** Task hash table item. */
  63. typedef struct {
  64.     link_t link;
  65.     task_id_t id;    /**< Task ID. */
  66.     bool destroyed;
  67. } hashed_task_t;
  68.  
  69. /** Compute hash index into task hash table.
  70.  *
  71.  * @param key Pointer keys. However, only the first key (i.e. truncated task
  72.  *            number) is used to compute the hash index.
  73.  *
  74.  * @return Hash index corresponding to key[0].
  75.  *
  76.  */
  77. static hash_index_t task_hash(unsigned long *key)
  78. {
  79.     assert(key);
  80.     return (LOWER32(*key) % TASK_HASH_TABLE_CHAINS);
  81. }
  82.  
  83. /** Compare a key with hashed item.
  84.  *
  85.  * @param key  Array of keys.
  86.  * @param keys Must be lesser or equal to 2.
  87.  * @param item Pointer to a hash table item.
  88.  *
  89.  * @return Non-zero if the key matches the item, zero otherwise.
  90.  *
  91.  */
  92. static int task_compare(unsigned long key[], hash_count_t keys, link_t *item)
  93. {
  94.     assert(key);
  95.     assert(keys <= 2);
  96.     assert(item);
  97.    
  98.     hashed_task_t *ht = hash_table_get_instance(item, hashed_task_t, link);
  99.    
  100.     if (keys == 2)
  101.         return ((LOWER32(key[1]) == UPPER32(ht->id))
  102.             && (LOWER32(key[0]) == LOWER32(ht->id)));
  103.     else
  104.         return (LOWER32(key[0]) == LOWER32(ht->id));
  105. }
  106.  
  107. /** Perform actions after removal of item from the hash table.
  108.  *
  109.  * @param item Item that was removed from the hash table.
  110.  *
  111.  */
  112. static void task_remove(link_t *item)
  113. {
  114.     assert(item);
  115.     free(hash_table_get_instance(item, hashed_task_t, link));
  116. }
  117.  
  118. /** Operations for task hash table. */
  119. static hash_table_operations_t task_hash_table_ops = {
  120.     .hash = task_hash,
  121.     .compare = task_compare,
  122.     .remove_callback = task_remove
  123. };
  124.  
  125. /** Task hash table structure. */
  126. static hash_table_t task_hash_table;
  127.  
  128. /** Pending task wait structure. */
  129. typedef struct {
  130.     link_t link;
  131.     task_id_t id;         /**< Task ID. */
  132.     ipc_callid_t callid;  /**< Call ID waiting for the connection */
  133. } pending_wait_t;
  134.  
  135. static link_t pending_wait;
  136.  
  137. int task_init(void)
  138. {
  139.     if (!hash_table_create(&task_hash_table, TASK_HASH_TABLE_CHAINS,
  140.         2, &task_hash_table_ops)) {
  141.         printf(NAME ": No memory available for tasks\n");
  142.         return ENOMEM;
  143.     }
  144.    
  145.     if (event_subscribe(EVENT_WAIT, 0) != EOK)
  146.         printf(NAME ": Error registering wait notifications\n");
  147.    
  148.     list_initialize(&pending_wait);
  149.    
  150.     return EOK;
  151. }
  152.  
  153. /** Process pending wait requests */
  154. void process_pending_wait(void)
  155. {
  156.     link_t *cur;
  157.    
  158. loop:
  159.     for (cur = pending_wait.next; cur != &pending_wait; cur = cur->next) {
  160.         pending_wait_t *pr = list_get_instance(cur, pending_wait_t, link);
  161.        
  162.         unsigned long keys[2] = {
  163.             LOWER32(pr->id),
  164.             UPPER32(pr->id)
  165.         };
  166.        
  167.         link_t *link = hash_table_find(&task_hash_table, keys);
  168.         if (!link)
  169.             continue;
  170.        
  171.         hashed_task_t *ht = hash_table_get_instance(link, hashed_task_t, link);
  172.         if (!ht->destroyed)
  173.             continue;
  174.        
  175.         if (!(pr->callid & IPC_CALLID_NOTIFICATION))
  176.             ipc_answer_0(pr->callid, EOK);
  177.        
  178.         hash_table_remove(&task_hash_table, keys, 2);
  179.         list_remove(cur);
  180.         free(pr);
  181.         goto loop;
  182.     }
  183. }
  184.  
  185. static void fail_pending_wait(task_id_t id, int rc)
  186. {
  187.     link_t *cur;
  188.    
  189. loop:
  190.     for (cur = pending_wait.next; cur != &pending_wait; cur = cur->next) {
  191.         pending_wait_t *pr = list_get_instance(cur, pending_wait_t, link);
  192.        
  193.         if (pr->id == id) {
  194.             if (!(pr->callid & IPC_CALLID_NOTIFICATION))
  195.                 ipc_answer_0(pr->callid, rc);
  196.        
  197.             list_remove(cur);
  198.             free(pr);
  199.             goto loop;
  200.         }
  201.     }
  202. }
  203.  
  204. void wait_notification(wait_type_t et, task_id_t id)
  205. {
  206.     unsigned long keys[2] = {
  207.         LOWER32(id),
  208.         UPPER32(id)
  209.     };
  210.    
  211.     link_t *link = hash_table_find(&task_hash_table, keys);
  212.    
  213.     if (link == NULL) {
  214.         hashed_task_t *ht =
  215.             (hashed_task_t *) malloc(sizeof(hashed_task_t));
  216.         if (ht == NULL) {
  217.             fail_pending_wait(id, ENOMEM);
  218.             return;
  219.         }
  220.        
  221.         link_initialize(&ht->link);
  222.         ht->id = id;
  223.         ht->destroyed = (et == TASK_CREATE) ? false : true;
  224.         hash_table_insert(&task_hash_table, keys, &ht->link);
  225.     } else {
  226.         hashed_task_t *ht =
  227.             hash_table_get_instance(link, hashed_task_t, link);
  228.         ht->destroyed = (et == TASK_CREATE) ? false : true;
  229.     }
  230. }
  231.  
  232. void wait_for_task(task_id_t id, ipc_call_t *call, ipc_callid_t callid)
  233. {
  234.     ipcarg_t retval;
  235.     unsigned long keys[2] = {
  236.         LOWER32(id),
  237.         UPPER32(id)
  238.     };
  239.    
  240.     link_t *link = hash_table_find(&task_hash_table, keys);
  241.     hashed_task_t *ht = (link != NULL) ?
  242.         hash_table_get_instance(link, hashed_task_t, link) : NULL;
  243.    
  244.     if ((ht == NULL) || (!ht->destroyed)) {
  245.         /* Add to pending list */
  246.         pending_wait_t *pr =
  247.             (pending_wait_t *) malloc(sizeof(pending_wait_t));
  248.         if (!pr) {
  249.             retval = ENOMEM;
  250.             goto out;
  251.         }
  252.        
  253.         pr->id = id;
  254.         pr->callid = callid;
  255.         list_append(&pr->link, &pending_wait);
  256.         return;
  257.     }
  258.    
  259.     hash_table_remove(&task_hash_table, keys, 2);
  260.     retval = EOK;
  261.    
  262. out:
  263.     if (!(callid & IPC_CALLID_NOTIFICATION))
  264.         ipc_answer_0(callid, retval);
  265. }
  266.  
  267. /**
  268.  * @}
  269.  */
  270.