Rev 29 | Go to most recent revision | Details | Compare with Previous | Last modification | View Log | RSS feed
| Rev | Author | Line No. | Line |
|---|---|---|---|
| 2 | pj | 1 | /* |
| 2 | * Project: S.Ha.R.K. |
||
| 3 | * |
||
| 4 | * Coordinators: |
||
| 5 | * Giorgio Buttazzo <giorgio@sssup.it> |
||
| 6 | * Paolo Gai <pj@gandalf.sssup.it> |
||
| 7 | * |
||
| 8 | * Authors : |
||
| 9 | * Paolo Gai <pj@gandalf.sssup.it> |
||
| 10 | * (see the web pages for full authors list) |
||
| 11 | * |
||
| 12 | * ReTiS Lab (Scuola Superiore S.Anna - Pisa - Italy) |
||
| 13 | * |
||
| 14 | * http://www.sssup.it |
||
| 15 | * http://retis.sssup.it |
||
| 16 | * http://shark.sssup.it |
||
| 17 | */ |
||
| 18 | |||
| 19 | /** |
||
| 20 | ------------ |
||
| 38 | pj | 21 | CVS : $Id: int_sem.c,v 1.3 2003-01-07 17:07:49 pj Exp $ |
| 2 | pj | 22 | |
| 23 | File: $File$ |
||
| 38 | pj | 24 | Revision: $Revision: 1.3 $ |
| 25 | Last update: $Date: 2003-01-07 17:07:49 $ |
||
| 2 | pj | 26 | ------------ |
| 27 | |||
| 28 | Internal semaphores. |
||
| 29 | |||
| 30 | They are different from the Posix semaphores and the mutexes because: |
||
| 31 | - internal_sem_wait is not a cancellation point |
||
| 32 | - there are no limits on the semaphores that can be created |
||
| 33 | (they works like a mutex_t...) |
||
| 34 | - the queuing policy is FIFO |
||
| 35 | - Be Careful! |
||
| 36 | they are made to be fast... so not so many controls are done!!! |
||
| 37 | |||
| 38 | **/ |
||
| 39 | |||
| 40 | /* |
||
| 41 | * Copyright (C) 2000 Paolo Gai |
||
| 42 | * |
||
| 43 | * This program is free software; you can redistribute it and/or modify |
||
| 44 | * it under the terms of the GNU General Public License as published by |
||
| 45 | * the Free Software Foundation; either version 2 of the License, or |
||
| 46 | * (at your option) any later version. |
||
| 47 | * |
||
| 48 | * This program is distributed in the hope that it will be useful, |
||
| 49 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
||
| 50 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
||
| 51 | * GNU General Public License for more details. |
||
| 52 | * |
||
| 53 | * You should have received a copy of the GNU General Public License |
||
| 54 | * along with this program; if not, write to the Free Software |
||
| 55 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
||
| 56 | * |
||
| 57 | */ |
||
| 58 | |||
| 59 | |||
| 60 | #include <kernel/int_sem.h> |
||
| 61 | #include <kernel/var.h> |
||
| 62 | #include <kernel/func.h> |
||
| 63 | |||
| 64 | /* Wait status for this library */ |
||
| 65 | #define INTERNAL_SEM_WAIT LIB_STATUS_BASE |
||
| 66 | |||
| 67 | |||
| 68 | void internal_sem_init(internal_sem_t *s, int value) |
||
| 69 | { |
||
| 70 | s->count = value; |
||
| 29 | pj | 71 | iq_init(&s->blocked,&freedesc,0); |
| 2 | pj | 72 | } |
| 73 | |||
| 74 | void internal_sem_wait(internal_sem_t *s) |
||
| 75 | { |
||
| 76 | SYS_FLAGS f; |
||
| 77 | |||
| 78 | //kern_cli(); |
||
| 79 | f = kern_fsave(); |
||
| 80 | |||
| 81 | if (s->count) { |
||
| 82 | s->count--; |
||
| 83 | //kern_sti(); |
||
| 84 | kern_frestore(f); |
||
| 85 | return; |
||
| 86 | } |
||
| 87 | else { /* We must block exec task */ |
||
| 88 | LEVEL l; /* for readableness only */ |
||
| 89 | |||
| 90 | proc_table[exec_shadow].context = kern_context_save(); |
||
| 38 | pj | 91 | |
| 92 | kern_epilogue_macro(); |
||
| 2 | pj | 93 | |
| 94 | l = proc_table[exec_shadow].task_level; |
||
| 38 | pj | 95 | level_table[l]->public_block(l,exec_shadow); |
| 2 | pj | 96 | |
| 97 | /* we insert the task in the semaphore queue */ |
||
| 98 | proc_table[exec_shadow].status = INTERNAL_SEM_WAIT; |
||
| 29 | pj | 99 | iq_insertlast(exec_shadow,&s->blocked); |
| 2 | pj | 100 | |
| 101 | /* and finally we reschedule */ |
||
| 102 | exec = exec_shadow = -1; |
||
| 103 | scheduler(); |
||
| 104 | |||
| 105 | ll_context_to(proc_table[exec_shadow].context); |
||
| 106 | kern_after_dispatch(); |
||
| 107 | kern_frestore(f); |
||
| 108 | } |
||
| 109 | |||
| 110 | } |
||
| 111 | |||
| 112 | /* return 0 if the counter is decremented, -1 if not */ |
||
| 113 | int internal_sem_trywait(internal_sem_t *s) |
||
| 114 | { |
||
| 115 | SYS_FLAGS f; |
||
| 116 | |||
| 117 | //kern_cli(); |
||
| 118 | f = kern_fsave(); |
||
| 119 | |||
| 120 | if (s->count) { |
||
| 121 | s->count--; |
||
| 122 | //kern_sti(); |
||
| 123 | kern_frestore(f); |
||
| 124 | return 0; |
||
| 125 | } |
||
| 126 | |||
| 127 | //kern_sti(); |
||
| 128 | kern_frestore(f); |
||
| 129 | return -1; |
||
| 130 | } |
||
| 131 | |||
| 132 | |||
| 133 | void internal_sem_post(internal_sem_t *s) |
||
| 134 | { |
||
| 135 | proc_table[exec_shadow].context = kern_context_save(); |
||
| 136 | |||
| 137 | if (s->blocked.first != -1) { |
||
| 138 | register PID p; |
||
| 139 | register LEVEL l; |
||
| 140 | |||
| 29 | pj | 141 | p = iq_getfirst(&s->blocked); |
| 2 | pj | 142 | l = proc_table[p].task_level; |
| 38 | pj | 143 | level_table[l]->public_unblock(l,p); |
| 2 | pj | 144 | |
| 145 | scheduler(); |
||
| 146 | } |
||
| 147 | else |
||
| 148 | s->count++; |
||
| 149 | |||
| 150 | kern_context_load(proc_table[exec_shadow].context); |
||
| 151 | } |
||
| 152 | |||
| 153 | int internal_sem_getvalue(internal_sem_t *s) |
||
| 154 | { |
||
| 155 | register int returnvalue; |
||
| 156 | SYS_FLAGS f; |
||
| 157 | |||
| 158 | //kern_cli(); |
||
| 159 | f = kern_fsave(); |
||
| 160 | if (s->blocked.first == -1) |
||
| 161 | returnvalue = s->count; |
||
| 162 | else |
||
| 163 | returnvalue = -1; |
||
| 164 | |||
| 165 | //kern_sti(); |
||
| 166 | kern_frestore(f); |
||
| 167 | return returnvalue; |
||
| 168 | } |