1 /*
2 * Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License as
6 * published by the Free Software Foundation; either version 2 of the
7 * License, or any later version.
8 *
9 * This program is distributed in the hope that it will be useful, but
10 * WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
17 */
18
19 FILE_LICENCE ( GPL2_OR_LATER );
20
21 #include <gpxe/list.h>
22 #include <gpxe/init.h>
23 #include <gpxe/process.h>
24
25 /** @file
26 *
27 * Processes
28 *
29 * We implement a trivial form of cooperative multitasking, in which
30 * all processes share a single stack and address space.
31 */
32
33 /** Process run queue */
34 static LIST_HEAD ( run_queue );
35
36 /**
37 * Add process to process list
38 *
39 * @v process Process
40 *
41 * It is safe to call process_add() multiple times; further calls will
42 * have no effect.
43 */
process_add(struct process * process)44 void process_add ( struct process *process ) {
45 if ( list_empty ( &process->list ) ) {
46 DBGC ( process, "PROCESS %p starting\n", process );
47 ref_get ( process->refcnt );
48 list_add_tail ( &process->list, &run_queue );
49 } else {
50 DBGC ( process, "PROCESS %p already started\n", process );
51 }
52 }
53
54 /**
55 * Remove process from process list
56 *
57 * @v process Process
58 *
59 * It is safe to call process_del() multiple times; further calls will
60 * have no effect.
61 */
process_del(struct process * process)62 void process_del ( struct process *process ) {
63 if ( ! list_empty ( &process->list ) ) {
64 DBGC ( process, "PROCESS %p stopping\n", process );
65 list_del ( &process->list );
66 INIT_LIST_HEAD ( &process->list );
67 ref_put ( process->refcnt );
68 } else {
69 DBGC ( process, "PROCESS %p already stopped\n", process );
70 }
71 }
72
73 /**
74 * Single-step a single process
75 *
76 * This executes a single step of the first process in the run queue,
77 * and moves the process to the end of the run queue.
78 */
step(void)79 void step ( void ) {
80 struct process *process;
81
82 list_for_each_entry ( process, &run_queue, list ) {
83 list_del ( &process->list );
84 list_add_tail ( &process->list, &run_queue );
85 DBGC2 ( process, "PROCESS %p executing\n", process );
86 process->step ( process );
87 DBGC2 ( process, "PROCESS %p finished executing\n", process );
88 break;
89 }
90 }
91
92 /**
93 * Initialise processes
94 *
95 */
init_processes(void)96 static void init_processes ( void ) {
97 struct process *process;
98
99 for_each_table_entry ( process, PERMANENT_PROCESSES )
100 process_add ( process );
101 }
102
103 /** Process initialiser */
104 struct init_fn process_init_fn __init_fn ( INIT_NORMAL ) = {
105 .initialise = init_processes,
106 };
107