src/core/process.c

   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  */
  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  */
  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  */
  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                 ref_get ( process->refcnt ); /* Inhibit destruction mid-step */
  86                 DBGC2 ( process, "PROCESS %p executing\n", process );
  87                 process->step ( process );
  88                 DBGC2 ( process, "PROCESS %p finished executing\n", process );
  89                 ref_put ( process->refcnt ); /* Allow destruction */
  90                 break;
  91         }
  92 }
  93
  94 /**
  95  * Initialise processes
  96  *
  97  */
  98 static void init_processes ( void ) {
  99         struct process *process;
 100
 101         for_each_table_entry ( process, PERMANENT_PROCESSES )
 102                 process_add ( process );
 103 }
 104
 105 /** Process initialiser */
 106 struct init_fn process_init_fn __init_fn ( INIT_NORMAL ) = {
 107         .initialise = init_processes,
 108 };