simplify osx_write_pre_select()
[paraslash.git] / sched.c
diff --git a/sched.c b/sched.c
index 879ab80..c2a0e64 100644 (file)
--- a/sched.c
+++ b/sched.c
@@ -1,3 +1,23 @@
+/*
+ * Copyright (C) 2006 Andre Noll <maan@systemlinux.org>
+ *
+ *     This program is free software; you can redistribute it and/or modify
+ *     it under the terms of the GNU General Public License as published by
+ *     the Free Software Foundation; either version 2 of the License, or
+ *     (at your option) any later version.
+ *
+ *     This program is distributed in the hope that it will be useful,
+ *     but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *     GNU General Public License for more details.
+ *
+ *     You should have received a copy of the GNU General Public License
+ *     along with this program; if not, write to the Free Software
+ *     Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
+ */
+
+/** \file sched.c paraslash's scheduling functions */
+
 #include <sys/time.h>
 #include "para.h"
 #include "ipc.h"
@@ -7,8 +27,11 @@
 #include "string.h"
 #include "error.h"
 
-struct list_head pre_select_list;
-struct list_head post_select_list;
+static struct list_head pre_select_list, post_select_list;
+static int initialized;
+
+static struct timeval now_struct;
+struct timeval *now = &now_struct;
 
 static void sched_preselect(struct sched *s)
 {
@@ -39,10 +62,24 @@ static void sched_post_select(struct sched *s)
        }
 }
 
+/**
+ * the core function for all paraslash programs
+ *
+ * Short and sweet. It updates the global \a now pointer, calls all registered
+ * pre_select hooks which may set the timeout and add any file descriptors to
+ * the fd sets of \a s.  Next, it calls para_select() and makes the result available
+ * to the registered tasks by calling their post_select hook.
+ *
+ * \return Zero if no more tasks are left in either of the two lists, negative
+ * if para_select returned an error.
+ *
+ * \sa task, now.
+ */
 int sched(struct sched *s)
 {
-
-       gettimeofday(&s->now, NULL);
+       if (!initialized)
+               return -E_NOT_INITIALIZED;
+       gettimeofday(now, NULL);
 again:
        FD_ZERO(&s->rfds);
        FD_ZERO(&s->wfds);
@@ -53,35 +90,61 @@ again:
                &s->wfds, &s->timeout);
        if (s->select_ret < 0)
                return s->select_ret;
-       gettimeofday(&s->now, NULL);
+       gettimeofday(now, NULL);
        sched_post_select(s);
        if (list_empty(&pre_select_list) && list_empty(&post_select_list))
                return 0;
        goto again;
 }
 
-void *register_task(struct task *t)
+/**
+ * initialize the paraslash scheduler
+ */
+static void init_sched(void)
+{
+       PARA_INFO_LOG("%s", "initializing scheduler\n");
+       INIT_LIST_HEAD(&pre_select_list);
+       INIT_LIST_HEAD(&post_select_list);
+       initialized = 1;
+};
+
+/**
+ * add a task to the scheduler
+ *
+ * \param t the task to add
+ *
+ * If the pre_select pointer of \a t is not \p NULL, it is added to
+ * the pre_select list of the scheduler. Same goes for post_select.
+ *
+ * \sa task::pre_select, task::post_select
+ */
+void register_task(struct task *t)
 {
+       if (!initialized)
+               init_sched();
        PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
        if (t->pre_select) {
                PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
-               if (t->flags & PRE_ADD_TAIL)
-                       list_add_tail(&t->pre_select_node, &pre_select_list);
-               else
-                       list_add(&t->pre_select_node, &pre_select_list);
+               list_add(&t->pre_select_node, &pre_select_list);
        }
        if (t->post_select) {
                PARA_DEBUG_LOG("post_select: %p\n", &t->pre_select);
-               if (t->flags & POST_ADD_TAIL)
-                       list_add_tail(&t->post_select_node, &post_select_list);
-               else
-                       list_add(&t->post_select_node, &post_select_list);
+               list_add(&t->post_select_node, &post_select_list);
        }
-       return t;
 }
 
+/**
+ * remove a task from the scheduler
+ *
+ * \param t the task to remove
+ *
+ * If the pre_select pointer of \a t is not \p NULL, it is removed from
+ * the pre_select list of the scheduler. Same goes for \a post_select.
+ */
 void unregister_task(struct task *t)
 {
+       if (!initialized)
+               return;
        PARA_INFO_LOG("unregistering %s (%p)\n", t->status, t);
        if (t->pre_select)
                list_del(&t->pre_select_node);
@@ -89,38 +152,53 @@ void unregister_task(struct task *t)
                list_del(&t->post_select_node);
 };
 
-void init_sched(void)
-{
-       INIT_LIST_HEAD(&pre_select_list);
-       INIT_LIST_HEAD(&post_select_list);
-};
-
+/**
+ * unregister all tasks
+ *
+ * This will cause \a sched() to return immediately because both the
+ * \a pre_select_list and the \a post_select_list are empty.
+ */
 void sched_shutdown(void)
 {
        struct task *t, *tmp;
 
+       if (!initialized)
+               return;
        list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node)
                unregister_task(t);
        /* remove tasks which do not have a pre_select hook */
        list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node)
                unregister_task(t);
+       initialized = 0;
 };
 
+/**
+ * get the list of all registered tasks.
+ *
+ * \return the task list
+ *
+ * Each entry of the list contains an identifier which is simply a hex number
+ * that may be used in \a kill_task() to terminate the task.
+ * The result ist dynamically allocated and must be freed by the caller.
+ */
 char *get_task_list(void)
 {
        struct task *t, *tmp;
        char *msg = NULL;
+
+       if (!initialized)
+               return NULL;
        list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
                char *tmp_msg;
-               tmp_msg = make_message("%s%p\t%s\n", msg? msg : "", t, t->status);
+               tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
                free(msg);
                msg = tmp_msg;
        }
        list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
                char *tmp_msg;
-               if (t->pre_select)
-                       continue;
-               tmp_msg = make_message("%s%p\t%s\n", msg? msg : "", t, t->status);
+//             if (t->pre_select)
+//                     continue;
+               tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
                free(msg);
                msg = tmp_msg;
        }
@@ -128,10 +206,24 @@ char *get_task_list(void)
        return msg;
 }
 
+/**
+ * simulate an error for the given task
+ *
+ * \param id the task identifier
+ *
+ * Find the task identified by \a id, set the tasks' return value to
+ * \p -E_TASK_KILLED and call the event handler of the task.
+ *
+ * \return Positive on success, negative on errors (e.g. if \a id does not
+ * correspond to a registered task).
+ */
 int kill_task(char *id)
 {
        struct task *t, *tmp;
        char buf[20];
+
+       if (!initialized)
+               return -E_NOT_INITIALIZED;
        list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
                sprintf(buf, "%p", t);
                if (strcmp(id, buf))