sched.c

   1 /*
   2  * Copyright (C) 2006-2008 Andre Noll <maan@systemlinux.org>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 /** \file sched.c paraslash's scheduling functions */
   8
   9 #include <dirent.h> /* readdir() */
  10 #include <assert.h>
  11 #include <sys/time.h>
  12
  13 #include "para.h"
  14 #include "ipc.h"
  15 #include "fd.h"
  16 #include "list.h"
  17 #include "sched.h"
  18 #include "string.h"
  19 #include "error.h"
  20
  21 static struct list_head pre_select_list, post_select_list;
  22 static int initialized;
  23
  24 static struct timeval now_struct;
  25 struct timeval *now = &now_struct;
  26
  27 /**
  28  * Remove a task from the scheduler.
  29  *
  30  * \param t the task to remove
  31  *
  32  * If the pre_select pointer of \a t is not \p NULL, it is removed from
  33  * the pre_select list of the scheduler. Same goes for \a post_select.
  34  */
  35 void unregister_task(struct task *t)
  36 {
  37         if (!initialized)
  38                 return;
  39         PARA_INFO_LOG("unregistering %s (%p)\n", t->status, t);
  40         if (t->pre_select)
  41                 list_del(&t->pre_select_node);
  42         if (t->post_select)
  43                 list_del(&t->post_select_node);
  44 };
  45
  46
  47 static void sched_preselect(struct sched *s)
  48 {
  49         struct task *t, *tmp;
  50         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
  51                 t->pre_select(s, t);
  52 //              PARA_INFO_LOG("%s \n", t->status);
  53                 if (t->error >= 0)
  54                         continue;
  55                 unregister_task(t);
  56         }
  57 }
  58
  59 static void sched_post_select(struct sched *s)
  60 {
  61         struct task *t, *tmp;
  62
  63         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
  64                 t->post_select(s, t);
  65 //              PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
  66                 if (t->error >= 0)
  67                         continue;
  68                 unregister_task(t);
  69         }
  70 }
  71
  72 /**
  73  * the core function for all paraslash programs
  74  *
  75  * \param s pointer to the scheduler struct
  76  *
  77  * This function updates the global \a now pointer, calls all registered
  78  * pre_select hooks which may set the timeout and add any file descriptors to
  79  * the fd sets of \a s.  Next, it calls para_select() and makes the result available
  80  * to the registered tasks by calling their post_select hook.
  81  *
  82  * \return Zero if no more tasks are left in either of the two lists, negative
  83  * if para_select returned an error.
  84  *
  85  * \sa task, now.
  86  */
  87 int schedule(struct sched *s)
  88 {
  89         int ret;
  90
  91         if (!initialized)
  92                 return -E_NOT_INITIALIZED;
  93         gettimeofday(now, NULL);
  94 again:
  95         FD_ZERO(&s->rfds);
  96         FD_ZERO(&s->wfds);
  97         s->timeout = s->default_timeout;
  98         s->max_fileno = -1;
  99         sched_preselect(s);
 100         ret = para_select(s->max_fileno + 1, &s->rfds, &s->wfds, &s->timeout);
 101         if (ret < 0)
 102                 return ret;
 103         gettimeofday(now, NULL);
 104         sched_post_select(s);
 105         if (list_empty(&pre_select_list) && list_empty(&post_select_list))
 106                 return 0;
 107         goto again;
 108 }
 109
 110 /**
 111  * initialize the paraslash scheduler
 112  */
 113 static void init_sched(void)
 114 {
 115         PARA_INFO_LOG("initializing scheduler\n");
 116         INIT_LIST_HEAD(&pre_select_list);
 117         INIT_LIST_HEAD(&post_select_list);
 118         initialized = 1;
 119 };
 120
 121 /**
 122  * add a task to the scheduler
 123  *
 124  * \param t the task to add
 125  *
 126  * If the pre_select pointer of \a t is not \p NULL, it is added to
 127  * the pre_select list of the scheduler. Same goes for post_select.
 128  *
 129  * \sa task::pre_select, task::post_select
 130  */
 131 void register_task(struct task *t)
 132 {
 133         if (!initialized)
 134                 init_sched();
 135         PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
 136         if (t->pre_select) {
 137                 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
 138                 list_add_tail(&t->pre_select_node, &pre_select_list);
 139         }
 140         if (t->post_select) {
 141                 PARA_DEBUG_LOG("post_select: %p\n", &t->pre_select);
 142                 list_add_tail(&t->post_select_node, &post_select_list);
 143         }
 144 }
 145
 146 /**
 147  * unregister all tasks
 148  *
 149  * This will cause \a schedule() to return immediately because both the
 150  * \a pre_select_list and the \a post_select_list are empty.
 151  */
 152 void sched_shutdown(void)
 153 {
 154         struct task *t, *tmp;
 155
 156         if (!initialized)
 157                 return;
 158         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node)
 159                 unregister_task(t);
 160         /* remove tasks which do not have a pre_select hook */
 161         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node)
 162                 unregister_task(t);
 163         initialized = 0;
 164 };
 165
 166 /**
 167  * get the list of all registered tasks.
 168  *
 169  * \return the task list
 170  *
 171  * Each entry of the list contains an identifier which is simply a hex number
 172  * that may be used in \a kill_task() to terminate the task.
 173  * The result ist dynamically allocated and must be freed by the caller.
 174  */
 175 char *get_task_list(void)
 176 {
 177         struct task *t, *tmp;
 178         char *msg = NULL;
 179
 180         if (!initialized)
 181                 return NULL;
 182         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
 183                 char *tmp_msg;
 184                 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
 185                 free(msg);
 186                 msg = tmp_msg;
 187         }
 188         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
 189                 char *tmp_msg;
 190 //              if (t->pre_select)
 191 //                      continue;
 192                 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
 193                 free(msg);
 194                 msg = tmp_msg;
 195         }
 196         //PARA_DEBUG_LOG("task list:\n%s", msg);
 197         return msg;
 198 }
 199
 200 /**
 201  * simulate an error for the given task
 202  *
 203  * \param id the task identifier
 204  *
 205  * Find the task identified by \a id, set the tasks' error value to
 206  * \p -E_TASK_KILLED and unregister the task.
 207  *
 208  * \return Positive on success, negative on errors (e.g. if \a id does not
 209  * correspond to a registered task).
 210  */
 211 int kill_task(char *id)
 212 {
 213         struct task *t, *tmp;
 214         char buf[20];
 215
 216         if (!initialized)
 217                 return -E_NOT_INITIALIZED;
 218         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
 219                 sprintf(buf, "%p", t);
 220                 if (strcmp(id, buf))
 221                         continue;
 222                 t->error = -E_TASK_KILLED;
 223                 unregister_task(t);
 224                 return 1;
 225         }
 226         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
 227                 sprintf(buf, "%p", t);
 228                 if (strcmp(id, buf))
 229                         continue;
 230                 t->error = -E_TASK_KILLED;
 231                 unregister_task(t);
 232                 return 1;
 233         }
 234         return -E_NO_SUCH_TASK;
 235 }