sched.h

   1 /*
   2  * Copyright (C) 2006-2011 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 select_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         /** If non-NULL, use this function instead of para_select. */
  31         int (*select_function)(int, fd_set *, fd_set *, struct timeval *);
  32         /** Currently active pre_select functions. */
  33         struct list_head pre_select_list;
  34         /** Currently active post_select functions. */
  35         struct list_head post_select_list;
  36 };
  37
  38 /**
  39  * Paraslash's task structure.
  40  *
  41  * Before registering a task to the scheduler, the task structure must be
  42  * filled in properly by the caller.
  43  *
  44  * If one of these functions sets \a t->error to a negative value, the
  45  * task gets unregistered automatically.
  46  *
  47  * \sa struct sched.
  48  */
  49 struct task {
  50         /**
  51          * The pre select hook of \a t.
  52          *
  53          * Its purpose is to add file descriptors to the fd sets of the
  54          * scheduler and to decrease the select timeout if necessary.
  55          */
  56         void (*pre_select)(struct sched *s, struct task *t);
  57         /**
  58          * The postselect hook of \a t.
  59          *
  60          * Evaluate and act upon the results of the previous select call.
  61          */
  62         void (*post_select)(struct sched *s, struct task *t);
  63         /** Whether this task is in error state. */
  64         int error;
  65         /** Position of the task in the pre_select list of the scheduler. */
  66         struct list_head pre_select_node;
  67         /** Position of the task in the post_select list of the scheduler. */
  68         struct list_head post_select_node;
  69         /** Descriptive text and current status of the task. */
  70         char status[255];
  71 };
  72
  73 /**
  74  * This is set by the scheduler at the beginning of its main loop.  It may be
  75  * used (read-only) from everywhere. As none of the functions called by the
  76  * scheduler are allowed to block, this value should be accurate enough so that
  77  * there is no need to call gettimeofday() directly.
  78  */
  79 extern struct timeval *now;
  80
  81 void register_task(struct sched *s, struct task *t);
  82 int schedule(struct sched *s);
  83 char *get_task_list(struct sched *s);
  84 void sched_shutdown(struct sched *s);
  85 void sched_min_delay(struct sched *s);
  86 void sched_request_timeout(struct timeval *to, struct sched *s);
  87 void sched_request_timeout_ms(long unsigned ms, struct sched *s);
  88 int sched_request_barrier(struct timeval *barrier, struct sched *s);
  89 int sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s);