sched.h

   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.h Sched and task structures and exported symbols from sched.c. */
   8
   9
  10 /**
  11  * Paraslash's scheduler.
  12  *
  13  * Designed with KISS in mind. It manages two lists of tasks.  The pre_select
  14  * list contains pointers to functions that are called before calling select()
  15  * from the main loop. Similarly, \a post_select_list is a list of function
  16  * pointers each of which is called after the select call. Tasks add hooks to
  17  * these lists by registering themselves to the scheduler.
  18  */
  19 struct sched {
  20         /** Initial value before any pre_select call. */
  21         struct timeval default_timeout;
  22         /** The current timeout for the upcoming select call. */
  23         struct timeval timeout;
  24         /** fds that should be watched for readability. */
  25         fd_set rfds;
  26         /** fds that should be watched for writability. */
  27         fd_set wfds;
  28         /** Highest numbered file descriptor in any of the above fd sets. */
  29         int max_fileno;
  30         /** In non-NULL, use this function instead of para_select. */
  31         int (*select_function)(int, fd_set *, fd_set *, struct timeval *);
  32 };
  33
  34 /**
  35  * Paraslash's task structure.
  36  *
  37  * Before registering a task to the scheduler, the task structure must be
  38  * filled in properly by the caller.
  39  *
  40  * If one of these functions sets \a t->error to a negative value, the
  41  * task gets unregistered automatically.
  42  *
  43  * \sa struct sched.
  44  */
  45 struct task {
  46         /**
  47          * The pre select hook of \a t.
  48          *
  49          * Its purpose is to add file descriptors to the fd sets of the
  50          * scheduler and to decrease the select timeout if necessary.
  51          */
  52         void (*pre_select)(struct sched *s, struct task *t);
  53         /**
  54          * The postselect hook of \a t.
  55          *
  56          * Evaluate and act upon the results of the previous select call.
  57          */
  58         void (*post_select)(struct sched *s, struct task *t);
  59         /** Whether this task is in error state. */
  60         int error;
  61         /** Position of the task in the pre_select list of the scheduler. */
  62         struct list_head pre_select_node;
  63         /** Position of the task in the post_select list of the scheduler. */
  64         struct list_head post_select_node;
  65         /** Descriptive text and current status of the task. */
  66         char status[MAXLINE];
  67 };
  68
  69 /**
  70  * This is set by the scheduler at the beginning of its main loop.  It may be
  71  * used (read-only) from everywhere. As none of the functions called by the
  72  * scheduler are allowed to block, this value should be accurate enough so that
  73  * there is no need to call gettimeofday() directly.
  74  */
  75 extern struct timeval *now;
  76
  77 void register_task(struct task *t);
  78 int schedule(struct sched *s);
  79 char *get_task_list(void);
  80 int kill_task(char *id);
  81 void sched_shutdown(void);