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Added basic code for implementing co-operative multitasking.

Yes, you really can do it in 65 bytes.
This commit is contained in:
Michael Brown 2006-04-29 16:42:09 +00:00
parent 5fe31f1014
commit 23c494d14e
2 changed files with 88 additions and 0 deletions

56
src/core/process.c Normal file
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/*
* Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
*
* 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 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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <gpxe/list.h>
#include <gpxe/process.h>
/** @file
*
* Processes
*
* We implement a trivial form of cooperative multitasking, in which
* all processes share a single stack and address space.
*/
/** Process run queue */
static LIST_HEAD ( run_queue );
/**
* Add process to run queue
*
* @v process Process
*/
void schedule ( struct process *process ) {
list_add_tail ( &process->list, &run_queue );
}
/**
* Single-step a single process
*
* This removes the first process from the run queue and executes a
* single step of that process.
*/
void step ( void ) {
struct process *process;
list_for_each_entry ( process, &run_queue, list ) {
list_del ( &process->list );
process->step ( process );
break;
}
}

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#ifndef _GPXE_PROCESS_H
#define _GPXE_PROCESS_H
/** @file
*
* Processes
*
*/
#include <gpxe/list.h>
/** A process */
struct process {
/** List of processes */
struct list_head list;
/**
* Single-step the process
*
* This method should execute a single step of the process.
* Returning from this method is isomorphic to yielding the
* CPU to another process.
*
* If the process wishes to be executed again, it must re-add
* itself to the run queue using schedule().
*/
void ( * step ) ( struct process *process );
};
extern void schedule ( struct process *process );
extern void step ( void );
#endif /* _GPXE_PROCESS_H */