sched.h

   1 /*
   2  * Copyright (C) 2006-2014 Andre Noll <maan@tuebingen.mpg.de>
   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 maintains a list of task structures which is
  14  * extended when a new task is registered. Each task may define a pre_select
  15  * function which is called from the scheduler main loop before it calls
  16  * select(). Similarly, each task must define a post_select function which is
  17  * called after the select call.
  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         /** Tasks which have been registered to the scheduler. */
  33         struct list_head task_list;
  34 };
  35
  36 struct task;
  37
  38 /** Information that must be supplied by callers of \ref task_register(). */
  39 struct task_info {
  40         /** Used for log messages and by \ref get_task_list(). */
  41         const char *name;
  42         /**
  43          * The optional pre select method.
  44          *
  45          * Its purpose is to add file descriptors to the fd sets of the
  46          * scheduler and to decrease the select timeout if necessary.
  47          */
  48         void (*pre_select)(struct sched *s, void *context);
  49         /**
  50          * The mandatory post select method.
  51          *
  52          * Its purpose is to evaluate and act upon the results of the previous
  53          * select call. If this function returns a negative value, the
  54          * scheduler unregisters the task.
  55          */
  56         int (*post_select)(struct sched *s, void *context);
  57         /**
  58          * This pointer is saved when the task is registered. It is passed to
  59          * ->pre_select() and ->post_select(). Usually this is a pointer to the
  60          * struct owned by the caller which contains the task pointer.
  61          */
  62         void *context;
  63 };
  64
  65 /**
  66  * This is set by the scheduler at the beginning of its main loop.  It may be
  67  * used (read-only) from everywhere. As none of the functions called by the
  68  * scheduler are allowed to block, this value should be accurate enough so that
  69  * there is no need to call clock_gettime() directly.
  70  */
  71 extern const struct timeval *now;
  72
  73 struct task *task_register(struct task_info *info, struct sched *s);
  74 int schedule(struct sched *s);
  75 void sched_shutdown(struct sched *s);
  76 char *get_task_list(struct sched *s);
  77 void task_notify(struct task *t, int err);
  78 void task_notify_all(struct sched *s, int err);
  79 int task_get_notification(const struct task *t);
  80 int task_status(const struct task *t);
  81 int task_reap(struct task **tptr);
  82 void sched_min_delay(struct sched *s);
  83 void sched_request_timeout(struct timeval *to, struct sched *s);
  84 void sched_request_timeout_ms(long unsigned ms, struct sched *s);
  85 int sched_request_barrier(struct timeval *barrier, struct sched *s);
  86 int sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s);