-/*
- * Copyright (C) 2006 Andre Noll <maan@systemlinux.org>
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111, USA.
- */
+/* Copyright (C) 2006 Andre Noll <maan@tuebingen.mpg.de>, see file COPYING. */
-/** \file sched.c Paraslash's task and scheduling functions */
+/** \file sched.h Sched and task structures and exported symbols from sched.c. */
/**
- * paraslash's scheduler
+ * Paraslash's scheduler.
+ *
+ * Designed with KISS in mind. It maintains a list of task structures which is
+ * extended when a new task is registered. Each task may define a pre_monitor
+ * function which is called from the scheduler main loop before it calls
+ * poll(2). Similarly, each task must define a post_monitor function which is
+ * called after poll(2) returns.
*
- * desinged with KISS in mind. It maintains two lists: The pre_select list
- * and the post_select list. Tasks add hokks to these lists by registering
- * themselves to the scheduler.
+ * \sa select(2), poll(2).
*/
struct sched {
- /** initial value before any pre_select call */
- struct timeval default_timeout;
- /** the current timeout for the upcoming select call */
- struct timeval timeout;
- /** fds that should be watched for readability */
- fd_set rfds;
- /** fds that should be watched for writability */
- fd_set wfds;
- /** highest numbered file descriptor in any of the above fd sets */
- int max_fileno;
- /** the return value of the previous select call */
- int select_ret;
+ /** Initial value (in milliseconds) before any pre_monitor call. */
+ int default_timeout;
+ /** The timeout (also in milliseconds) for the next iteration. */
+ int timeout;
+ /** Passed to poll(2). */
+ struct pollfd *pfd;
+ /** Number of elements in the above array, passed to poll(2). */
+ unsigned pfd_array_len;
+ /** Number of fds registered for montitoring so far. */
+ unsigned num_pfds;
+ /** Maps fds to indices of the pfd array. */
+ unsigned *pidx;
+ /** Mumber of elements in the above pidx array. */
+ unsigned pidx_array_len;
+ /** If non-NULL, use this function instead of \ref xpoll(). */
+ int (*poll_function)(struct pollfd *fds, nfds_t nfds, int timeout);
+ /** Tasks which have been registered to the scheduler. */
+ struct list_head task_list;
};
-/**
- * paraslash's task structure
- *
- * before registering a task to the scheduler, the task structure must be
- * filled in properly by the caller.
- *
- * The pre_select or the post_select pointer, but not both may be NULL. Once
- * a task is registered, its pre_select and post_select function gets called
- * from the scheduler's mainloop. The purpose of the pre_select loop is to add
- * file descriptors to the fd sets of the scheduler and to decrease the select
- * timeout if neccessary. The post_select function may then evaluate these fd
- * sets and act upon the results.
+struct task;
- * If one of these functions return a negative value via \a t->ret the
- * (optional) event_handler gets called (it may also be called in case another
- * event happend). In many cases the only possible event is an error or an eof
- * condition and the event handler simply unregisters the task from the
- * scheduler.
- *
- * \sa struct sched
- */
-struct task {
- /** pointer to the struct this task is embedded in */
- void *private_data;
- /** pre_select hook */
- void (*pre_select)(struct sched *s, struct task *t);
- /** post_select hook */
- void (*post_select)(struct sched *s, struct task *t);
- /** gets called */
- void (*event_handler)(struct task *t);
- /** pre_select() and post_select store their return value here */
- int ret;
- /** position of the task in the pre_select list of the scheduler */
- struct list_head pre_select_node;
- /** position of the task in the post_select list of the scheduler */
- struct list_head post_select_node;
- /** descriptive text and current status of the task */
- char status[MAXLINE];
+/** Information that must be supplied by callers of \ref task_register(). */
+struct task_info {
+ /** Used for log messages and by \ref get_task_list(). */
+ const char *name;
+ /**
+ * Configure watch fds and impose an upper bound on the I/O timeout.
+ *
+ * If this is not NULL, the function is called at each iteration of the
+ * scheduler's main loop. Its purpose is to tell the scheduler that
+ * certain file descriptors should be monitored for readiness for I/O.
+ * The function may also lower the scheduler's timeout value (but shall
+ * never increase it) to impose an upper bound on the waiting time in
+ * case no file descriptors happen to be ready.
+ *
+ * \sa \ref time.c.
+ */
+ void (*pre_monitor)(struct sched *s, void *context);
+ /**
+ * Perform I/O on file descriptors which are ready for I/O.
+ *
+ * This mandatory hook is called after the system call which monitors
+ * file descriptors returns. The function should perform non-blocking
+ * I/O on those file descriptors which are reported as being ready.
+ *
+ * If this function returns a negative value, the scheduler unregisters
+ * the task.
+ */
+ int (*post_monitor)(struct sched *s, void *context);
+ /**
+ * This pointer is saved when the task is registered. It is passed to
+ * ->pre_monitor() and ->post_monitor(). Usually this is a pointer to the
+ * struct owned by the caller which contains the task pointer.
+ */
+ void *context;
};
/**
* This is set by the scheduler at the beginning of its main loop. It may be
* used (read-only) from everywhere. As none of the functions called by the
* scheduler are allowed to block, this value should be accurate enough so that
- * there is no need to call gettimeofday() directly.
+ * there is no need to call clock_gettime() directly.
*/
-extern struct timeval *now;
+extern const struct timeval *now;
-void *register_task(struct task *t);
-void unregister_task(struct task *t);
-int sched(struct sched *s);
-void init_sched(void);
-char *get_task_list(void);
-int kill_task(char *id);
+struct task *task_register(struct task_info *info, struct sched *s);
+int schedule(struct sched *s);
+void sched_shutdown(struct sched *s);
+char *get_task_list(struct sched *s);
+void task_notify(struct task *t, int err);
+void task_notify_all(struct sched *s, int err);
+int task_get_notification(const struct task *t);
+int task_status(const struct task *t);
+int task_reap(struct task **tptr);
+void sched_min_delay(struct sched *s);
+void sched_request_timeout(struct timeval *to, struct sched *s);
+void sched_request_timeout_ms(long unsigned ms, struct sched *s);
+int sched_request_barrier(struct timeval *barrier, struct sched *s);
+int sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s);
+void sched_monitor_readfd(int fd, struct sched *s);
+void sched_monitor_writefd(int fd, struct sched *s);
+bool sched_read_ok(int fd, const struct sched *s);
+bool sched_write_ok(int fd, const struct sched *s);
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