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 #include <gpxe/list.h>
  20 #include <gpxe/init.h>
  21 #include <gpxe/process.h>
  22
  23 /** @file
  24  *
  25  * Processes
  26  *
  27  * We implement a trivial form of cooperative multitasking, in which
  28  * all processes share a single stack and address space.
  29  */
  30
  31 /** Process run queue */
  32 static LIST_HEAD ( run_queue );
  33
  34 /** Registered permanent processes */
  35 static struct process processes[0]
  36         __table_start ( struct process, processes );
  37 static struct process processes_end[0]
  38         __table_end ( struct process, processes );
  39
  40 /**
  41  * Add process to process list
  42  *
  43  * @v process           Process
  44  */
  45 void process_add ( struct process *process ) {
  46         ref_get ( process->refcnt );
  47         list_add_tail ( &process->list, &run_queue );
  48 }
  49
  50 /**
  51  * Remove process from process list
  52  *
  53  * @v process           Process
  54  *
  55  * It is safe to call process_del() multiple times; further calls will
  56  * have no effect.
  57  */
  58 void process_del ( struct process *process ) {
  59         if ( ! list_empty ( &process->list ) ) {
  60                 list_del ( &process->list );
  61                 INIT_LIST_HEAD ( &process->list );
  62                 ref_put ( process->refcnt );
  63         }
  64 }
  65
  66 /**
  67  * Single-step a single process
  68  *
  69  * This executes a single step of the first process in the run queue,
  70  * and moves the process to the end of the run queue.
  71  */
  72 void step ( void ) {
  73         struct process *process;
  74
  75         list_for_each_entry ( process, &run_queue, list ) {
  76                 list_del ( &process->list );
  77                 list_add_tail ( &process->list, &run_queue );
  78                 process->step ( process );
  79                 break;
  80         }
  81 }
  82
  83 /**
  84  * Initialise processes
  85  *
  86  */
  87 static void init_processes ( void ) {
  88         struct process *process;
  89
  90         for ( process = processes ; process < processes_end ; process++ ) {
  91                 process_add ( process );
  92         }
  93 }
  94
  95 /** Process initialiser */
  96 struct init_fn process_init_fn __init_fn ( INIT_NORMAL ) = {
  97         .initialise = init_processes,
  98 };