sched.h

   1 /* Copyright (C) 2006 Andre Noll <maan@tuebingen.mpg.de>, see file COPYING. */
   2
   3 /** \file sched.h Sched and task structures and exported symbols from sched.c. */
   4
   5
   6 /**
   7  * Paraslash's scheduler.
   8  *
   9  * Designed with KISS in mind. It maintains a list of task structures which is
  10  * extended when a new task is registered. Each task may define a pre_select
  11  * function which is called from the scheduler main loop before it calls
  12  * select(). Similarly, each task must define a post_select function which is
  13  * called after the select call.
  14  */
  15 struct sched {
  16         /** Initial value before any pre_select call. */
  17         struct timeval default_timeout;
  18         /** The current timeout for the upcoming select call. */
  19         struct timeval select_timeout;
  20         /** fds that should be watched for readability. */
  21         fd_set rfds;
  22         /** fds that should be watched for writability. */
  23         fd_set wfds;
  24         /** Highest numbered file descriptor in any of the above fd sets. */
  25         int max_fileno;
  26         /** If non-NULL, use this function instead of para_select. */
  27         int (*select_function)(int, fd_set *, fd_set *, struct timeval *);
  28         /** Tasks which have been registered to the scheduler. */
  29         struct list_head task_list;
  30 };
  31
  32 struct task;
  33
  34 /** Information that must be supplied by callers of \ref task_register(). */
  35 struct task_info {
  36         /** Used for log messages and by \ref get_task_list(). */
  37         const char *name;
  38         /**
  39          * The optional pre select method.
  40          *
  41          * Its purpose is to add file descriptors to the fd sets of the
  42          * scheduler and to decrease the select timeout if necessary.
  43          */
  44         void (*pre_select)(struct sched *s, void *context);
  45         /**
  46          * The mandatory post select method.
  47          *
  48          * Its purpose is to evaluate and act upon the results of the previous
  49          * select call. If this function returns a negative value, the
  50          * scheduler unregisters the task.
  51          */
  52         int (*post_select)(struct sched *s, void *context);
  53         /**
  54          * This pointer is saved when the task is registered. It is passed to
  55          * ->pre_select() and ->post_select(). Usually this is a pointer to the
  56          * struct owned by the caller which contains the task pointer.
  57          */
  58         void *context;
  59 };
  60
  61 /**
  62  * This is set by the scheduler at the beginning of its main loop.  It may be
  63  * used (read-only) from everywhere. As none of the functions called by the
  64  * scheduler are allowed to block, this value should be accurate enough so that
  65  * there is no need to call clock_gettime() directly.
  66  */
  67 extern const struct timeval *now;
  68
  69 struct task *task_register(struct task_info *info, struct sched *s);
  70 int schedule(struct sched *s);
  71 void sched_shutdown(struct sched *s);
  72 char *get_task_list(struct sched *s);
  73 void task_notify(struct task *t, int err);
  74 void task_notify_all(struct sched *s, int err);
  75 int task_get_notification(const struct task *t);
  76 int task_status(const struct task *t);
  77 int task_reap(struct task **tptr);
  78 void sched_min_delay(struct sched *s);
  79 void sched_request_timeout(struct timeval *to, struct sched *s);
  80 void sched_request_timeout_ms(long unsigned ms, struct sched *s);
  81 int sched_request_barrier(struct timeval *barrier, struct sched *s);
  82 int sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s);