sched.h

   1 /*
   2  * Copyright (C) 2006 Andre Noll <maan@systemlinux.org>
   3  *
   4  *     This program is free software; you can redistribute it and/or modify
   5  *     it under the terms of the GNU General Public License as published by
   6  *     the Free Software Foundation; either version 2 of the License, or
   7  *     (at your option) any later version.
   8  *
   9  *     This program is distributed in the hope that it will be useful,
  10  *     but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  *     GNU General Public License for more details.
  13  *
  14  *     You should have received a copy of the GNU General Public License
  15  *     along with this program; if not, write to the Free Software
  16  *     Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
  17  */
  18
  19 /** \file sched.c Paraslash's task and scheduling functions */
  20
  21
  22 /**
  23  * paraslash's scheduler
  24  *
  25  * desinged with KISS in mind. It maintains two lists: The pre_select list
  26  * and the post_select list. Tasks add hokks to these lists by registering
  27  * themselves to the scheduler.
  28  */
  29 struct sched {
  30         /** initial value before any pre_select call */
  31         struct timeval default_timeout;
  32         /** the current timeout for the upcoming select call */
  33         struct timeval timeout;
  34         /** fds that should be watched for readability */
  35         fd_set rfds;
  36         /** fds that should be watched for writability */
  37         fd_set wfds;
  38         /** highest numbered file descriptor in any of the above fd sets */
  39         int max_fileno;
  40         /** the return value of the previous select call */
  41         int select_ret;
  42 };
  43
  44 /**
  45  * paraslash's task structure
  46  *
  47  * before registering a task to the scheduler, the task structure must be
  48  * filled in properly by the caller.
  49  *
  50  * The  pre_select or the post_select pointer, but not both may be NULL.  Once
  51  * a task is registered, its pre_select and post_select function gets called
  52  * from the scheduler's mainloop. The purpose of the pre_select loop is to add
  53  * file descriptors to the fd sets of the scheduler and to decrease the select
  54  * timeout if neccessary. The post_select function may then evaluate these fd
  55  * sets and act upon the results.
  56
  57  * If one of these functions return a negative value via \a t->ret the
  58  * (optional) event_handler gets called (it may also be called in case another
  59  * event happend). In many cases the only possible event is an error or an eof
  60  * condition and the event handler simply unregisters the task from the
  61  * scheduler.
  62  *
  63  * \sa struct sched
  64  */
  65 struct task {
  66         /** pointer to the struct this task is embedded in */
  67         void *private_data;
  68         /** pre_select hook */
  69         void (*pre_select)(struct sched *s, struct task *t);
  70         /** post_select hook */
  71         void (*post_select)(struct sched *s, struct task *t);
  72         /** gets called */
  73         void (*event_handler)(struct task *t);
  74         /** pre_select() and post_select store their return value here */
  75         int ret;
  76         /** position of the task in the pre_select list of the scheduler */
  77         struct list_head pre_select_node;
  78         /** position of the task in the post_select list of the scheduler */
  79         struct list_head post_select_node;
  80         /** descriptive text and current status of the task */
  81         char status[MAXLINE];
  82 };
  83
  84 /**
  85  * This is set by the scheduler at the beginning of its main loop.  It may be
  86  * used (read-only) from everywhere. As none of the functions called by the
  87  * scheduler are allowed to block, this value should be accurate enough so that
  88  * there is no need to call gettimeofday() directly.
  89  */
  90 extern struct timeval *now;
  91
  92 void *register_task(struct task *t);
  93 void unregister_task(struct task *t);
  94 int sched(struct sched *s);
  95 void init_sched(void);
  96 char *get_task_list(void);
  97 int kill_task(char *id);