ccc2655540
Some processes execute only once, and exist solely in order to defer execution until after the relevant instantiator method has returned. Such processes do not need to be automatically rescheduled when executing. Signed-off-by: Michael Brown <mcb30@ipxe.org>
133 lines
3.6 KiB
C
133 lines
3.6 KiB
C
/*
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* Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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FILE_LICENCE ( GPL2_OR_LATER );
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#include <ipxe/list.h>
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#include <ipxe/init.h>
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#include <ipxe/process.h>
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/** @file
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*
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* Processes
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*
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* We implement a trivial form of cooperative multitasking, in which
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* all processes share a single stack and address space.
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*/
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/** Process run queue */
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static LIST_HEAD ( run_queue );
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/**
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* Get pointer to object containing process
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*
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* @v process Process
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* @ret object Containing object
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*/
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void * process_object ( struct process *process ) {
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return ( ( ( void * ) process ) - process->desc->offset );
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}
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/**
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* Add process to process list
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*
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* @v process Process
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*
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* It is safe to call process_add() multiple times; further calls will
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* have no effect.
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*/
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void process_add ( struct process *process ) {
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if ( ! process_running ( process ) ) {
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DBGC ( PROC_COL ( process ), "PROCESS " PROC_FMT
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" starting\n", PROC_DBG ( process ) );
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ref_get ( process->refcnt );
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list_add_tail ( &process->list, &run_queue );
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} else {
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DBGC ( PROC_COL ( process ), "PROCESS " PROC_FMT
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" already started\n", PROC_DBG ( process ) );
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}
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}
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/**
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* Remove process from process list
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*
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* @v process Process
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*
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* It is safe to call process_del() multiple times; further calls will
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* have no effect.
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*/
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void process_del ( struct process *process ) {
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if ( process_running ( process ) ) {
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DBGC ( PROC_COL ( process ), "PROCESS " PROC_FMT
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" stopping\n", PROC_DBG ( process ) );
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list_del ( &process->list );
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INIT_LIST_HEAD ( &process->list );
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ref_put ( process->refcnt );
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} else {
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DBGC ( PROC_COL ( process ), "PROCESS " PROC_FMT
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" already stopped\n", PROC_DBG ( process ) );
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}
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}
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/**
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* Single-step a single process
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*
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* This executes a single step of the first process in the run queue,
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* and moves the process to the end of the run queue.
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*/
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void step ( void ) {
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struct process *process;
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struct process_descriptor *desc;
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void *object;
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if ( ( process = list_first_entry ( &run_queue, struct process,
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list ) ) ) {
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ref_get ( process->refcnt ); /* Inhibit destruction mid-step */
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desc = process->desc;
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object = process_object ( process );
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if ( desc->reschedule ) {
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list_del ( &process->list );
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list_add_tail ( &process->list, &run_queue );
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} else {
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process_del ( process );
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}
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DBGC2 ( PROC_COL ( process ), "PROCESS " PROC_FMT
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" executing\n", PROC_DBG ( process ) );
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desc->step ( object );
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DBGC2 ( PROC_COL ( process ), "PROCESS " PROC_FMT
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" finished executing\n", PROC_DBG ( process ) );
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ref_put ( process->refcnt ); /* Allow destruction */
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}
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}
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/**
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* Initialise processes
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*
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*/
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static void init_processes ( void ) {
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struct process *process;
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for_each_table_entry ( process, PERMANENT_PROCESSES )
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process_add ( process );
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}
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/** Process initialiser */
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struct init_fn process_init_fn __init_fn ( INIT_NORMAL ) = {
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.initialise = init_processes,
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};
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