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| 2 | pj | 1 | /* |
| 2 | * Project: S.Ha.R.K. |
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| 3 | * |
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| 4 | * Coordinators: |
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| 5 | * Giorgio Buttazzo <giorgio@sssup.it> |
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| 6 | * Paolo Gai <pj@gandalf.sssup.it> |
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| 7 | * |
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| 8 | * Authors : |
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| 9 | * Paolo Gai <pj@gandalf.sssup.it> |
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| 10 | * (see the web pages for full authors list) |
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| 11 | * |
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| 12 | * ReTiS Lab (Scuola Superiore S.Anna - Pisa - Italy) |
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| 13 | * |
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| 14 | * http://www.sssup.it |
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| 15 | * http://retis.sssup.it |
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| 16 | * http://shark.sssup.it |
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| 17 | */ |
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| 18 | |||
| 19 | /** |
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| 20 | ------------ |
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| 318 | giacomo | 21 | CVS : $Id: int_sem.c,v 1.4 2003-11-05 15:05:11 giacomo Exp $ |
| 2 | pj | 22 | |
| 23 | File: $File$ |
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| 318 | giacomo | 24 | Revision: $Revision: 1.4 $ |
| 25 | Last update: $Date: 2003-11-05 15:05:11 $ |
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| 2 | pj | 26 | ------------ |
| 27 | |||
| 28 | Internal semaphores. |
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| 29 | |||
| 30 | They are different from the Posix semaphores and the mutexes because: |
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| 31 | - internal_sem_wait is not a cancellation point |
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| 32 | - there are no limits on the semaphores that can be created |
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| 33 | (they works like a mutex_t...) |
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| 34 | - the queuing policy is FIFO |
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| 35 | - Be Careful! |
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| 36 | they are made to be fast... so not so many controls are done!!! |
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| 37 | |||
| 38 | **/ |
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| 39 | |||
| 40 | /* |
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| 41 | * Copyright (C) 2000 Paolo Gai |
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| 42 | * |
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| 43 | * This program is free software; you can redistribute it and/or modify |
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| 44 | * it under the terms of the GNU General Public License as published by |
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| 45 | * the Free Software Foundation; either version 2 of the License, or |
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| 46 | * (at your option) any later version. |
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| 47 | * |
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| 48 | * This program is distributed in the hope that it will be useful, |
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| 49 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 50 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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| 51 | * GNU General Public License for more details. |
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| 52 | * |
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| 53 | * You should have received a copy of the GNU General Public License |
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| 54 | * along with this program; if not, write to the Free Software |
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| 55 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
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| 56 | * |
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| 57 | */ |
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| 58 | |||
| 59 | |||
| 60 | #include <kernel/int_sem.h> |
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| 61 | #include <kernel/var.h> |
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| 62 | #include <kernel/func.h> |
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| 63 | |||
| 64 | /* Wait status for this library */ |
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| 65 | #define INTERNAL_SEM_WAIT LIB_STATUS_BASE |
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| 66 | |||
| 67 | |||
| 68 | void internal_sem_init(internal_sem_t *s, int value) |
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| 69 | { |
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| 70 | s->count = value; |
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| 29 | pj | 71 | iq_init(&s->blocked,&freedesc,0); |
| 2 | pj | 72 | } |
| 73 | |||
| 74 | void internal_sem_wait(internal_sem_t *s) |
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| 75 | { |
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| 76 | SYS_FLAGS f; |
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| 77 | |||
| 78 | f = kern_fsave(); |
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| 79 | |||
| 80 | if (s->count) { |
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| 81 | s->count--; |
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| 82 | kern_frestore(f); |
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| 83 | return; |
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| 84 | } |
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| 85 | else { /* We must block exec task */ |
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| 86 | LEVEL l; /* for readableness only */ |
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| 87 | |||
| 88 | proc_table[exec_shadow].context = kern_context_save(); |
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| 38 | pj | 89 | |
| 90 | kern_epilogue_macro(); |
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| 2 | pj | 91 | |
| 92 | l = proc_table[exec_shadow].task_level; |
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| 38 | pj | 93 | level_table[l]->public_block(l,exec_shadow); |
| 2 | pj | 94 | |
| 95 | /* we insert the task in the semaphore queue */ |
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| 96 | proc_table[exec_shadow].status = INTERNAL_SEM_WAIT; |
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| 29 | pj | 97 | iq_insertlast(exec_shadow,&s->blocked); |
| 2 | pj | 98 | |
| 99 | /* and finally we reschedule */ |
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| 100 | exec = exec_shadow = -1; |
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| 101 | scheduler(); |
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| 102 | |||
| 103 | ll_context_to(proc_table[exec_shadow].context); |
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| 104 | kern_after_dispatch(); |
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| 105 | kern_frestore(f); |
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| 106 | } |
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| 107 | |||
| 108 | } |
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| 109 | |||
| 110 | /* return 0 if the counter is decremented, -1 if not */ |
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| 111 | int internal_sem_trywait(internal_sem_t *s) |
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| 112 | { |
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| 113 | SYS_FLAGS f; |
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| 114 | |||
| 115 | f = kern_fsave(); |
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| 116 | |||
| 117 | if (s->count) { |
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| 118 | s->count--; |
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| 119 | kern_frestore(f); |
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| 120 | return 0; |
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| 121 | } |
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| 122 | |||
| 123 | return -1; |
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| 124 | } |
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| 125 | |||
| 126 | |||
| 127 | void internal_sem_post(internal_sem_t *s) |
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| 128 | { |
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| 129 | proc_table[exec_shadow].context = kern_context_save(); |
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| 130 | |||
| 131 | if (s->blocked.first != -1) { |
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| 132 | register PID p; |
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| 133 | register LEVEL l; |
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| 134 | |||
| 29 | pj | 135 | p = iq_getfirst(&s->blocked); |
| 2 | pj | 136 | l = proc_table[p].task_level; |
| 38 | pj | 137 | level_table[l]->public_unblock(l,p); |
| 2 | pj | 138 | |
| 139 | scheduler(); |
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| 140 | } |
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| 141 | else |
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| 142 | s->count++; |
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| 143 | |||
| 144 | kern_context_load(proc_table[exec_shadow].context); |
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| 145 | } |
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| 146 | |||
| 147 | int internal_sem_getvalue(internal_sem_t *s) |
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| 148 | { |
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| 149 | register int returnvalue; |
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| 150 | SYS_FLAGS f; |
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| 151 | |||
| 152 | f = kern_fsave(); |
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| 153 | if (s->blocked.first == -1) |
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| 154 | returnvalue = s->count; |
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| 155 | else |
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| 156 | returnvalue = -1; |
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| 157 | |||
| 158 | kern_frestore(f); |
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| 159 | return returnvalue; |
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| 160 | } |