From: Andre <maan@p133.(none)>
Date: Mon, 12 Jun 2006 13:17:06 +0000 (+0200)
Subject: Add scheduler documentation
X-Git-Tag: v0.2.14~62^2~15
X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=commitdiff_plain;h=bc5f28a9274c3b8ed5086399cec3b1c9b3e250b9

Add scheduler documentation

and a GPL header
---

diff --git a/sched.h b/sched.h
index bd1ad796..8a6ed1a8 100644
--- a/sched.h
+++ b/sched.h
@@ -1,22 +1,92 @@
+/*
+ * 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.
+ */
+
+/** \file sched.c Paraslash's task and scheduling functions */
+
+
+/**
+ * paraslash's scheduler
+ *
+ * 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.
+ */
 struct sched {
-	struct timeval now, timeout;
+	/** 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;
-	fd_set rfds, wfds;
+	/** the return value of the previous select call */
 	int select_ret;
-	struct timeval default_timeout;
 };
 
+/**
+ * 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.
+
+ * 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;
-	int ret;
+	/** 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];
 };
 
+/**
+ * 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.
+ */
 extern struct timeval *now;
 
 void *register_task(struct task *t);