source: mainline/uspace/lib/libc/generic/fibril.c@ aadf01e

lfn serial ticket/834-toolchain-update topic/msim-upgrade topic/simplify-dev-export
Last change on this file since aadf01e was f41aa81, checked in by Jakub Jermar <jakub@…>, 15 years ago

Remove a confusing comment and a dirty hack.
  • Property mode set to 100644
File size: 8.7 KB
Line 
1/*
2 * Copyright (c) 2006 Ondrej Palkovsky
3 * Copyright (c) 2007 Jakub Jermar
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 *
10 * - Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * - Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * - The name of the author may not be used to endorse or promote products
16 * derived from this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
23 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 */
29
30/** @addtogroup libc
31 * @{
32 */
33/** @file
34 */
35
36#include <adt/list.h>
37#include <fibril.h>
38#include <thread.h>
39#include <tls.h>
40#include <malloc.h>
41#include <unistd.h>
42#include <stdio.h>
43#include <arch/barrier.h>
44#include <libarch/faddr.h>
45#include <futex.h>
46#include <assert.h>
47#include <async.h>
48
49#ifndef FIBRIL_INITIAL_STACK_PAGES_NO
50#define FIBRIL_INITIAL_STACK_PAGES_NO 1
51#endif
52
53/**
54 * This futex serializes access to ready_list, serialized_list and manager_list.
55 */
56static atomic_t fibril_futex = FUTEX_INITIALIZER;
57
58static LIST_INITIALIZE(ready_list);
59static LIST_INITIALIZE(serialized_list);
60static LIST_INITIALIZE(manager_list);
61
62static void fibril_main(void);
63
64/** Number of threads that are executing a manager fibril. */
65static int threads_in_manager;
66/** Number of threads that are executing a manager fibril and are serialized. */
67static int serialized_threads; /* Protected by async_futex */
68/** Fibril-local count of serialization. If > 0, we must not preempt */
69static fibril_local int serialization_count;
70
71/** Setup fibril information into TCB structure */
72fibril_t *fibril_setup(void)
73{
74 fibril_t *f;
75 tcb_t *tcb;
76
77 tcb = __make_tls();
78 if (!tcb)
79 return NULL;
80
81 f = malloc(sizeof(fibril_t));
82 if (!f) {
83 __free_tls(tcb);
84 return NULL;
85 }
86
87 tcb->fibril_data = f;
88 f->tcb = tcb;
89
90 f->func = NULL;
91 f->arg = NULL;
92 f->stack = NULL;
93 f->clean_after_me = NULL;
94 f->retval = 0;
95 f->flags = 0;
96
97 return f;
98}
99
100void fibril_teardown(fibril_t *f)
101{
102 __free_tls(f->tcb);
103 free(f);
104}
105
106/** Function that spans the whole life-cycle of a fibril.
107 *
108 * Each fibril begins execution in this function. Then the function implementing
109 * the fibril logic is called. After its return, the return value is saved.
110 * The fibril then switches to another fibril, which cleans up after it.
111 */
112void fibril_main(void)
113{
114 fibril_t *f = __tcb_get()->fibril_data;
115
116 /* Call the implementing function. */
117 f->retval = f->func(f->arg);
118
119 fibril_switch(FIBRIL_FROM_DEAD);
120 /* not reached */
121}
122
123/** Switch from the current fibril.
124 *
125 * If calling with FIBRIL_TO_MANAGER parameter, the async_futex should be
126 * held.
127 *
128 * @param stype Switch type. One of FIBRIL_PREEMPT, FIBRIL_TO_MANAGER,
129 * FIBRIL_FROM_MANAGER, FIBRIL_FROM_DEAD. The parameter
130 * describes the circumstances of the switch.
131 * @return Return 0 if there is no ready fibril,
132 * return 1 otherwise.
133 */
134int fibril_switch(fibril_switch_type_t stype)
135{
136 int retval = 0;
137
138 futex_down(&fibril_futex);
139
140 if (stype == FIBRIL_PREEMPT && list_empty(&ready_list))
141 goto ret_0;
142
143 if (stype == FIBRIL_FROM_MANAGER) {
144 if ((list_empty(&ready_list)) && (list_empty(&serialized_list)))
145 goto ret_0;
146
147 /*
148 * Do not preempt if there is not enough threads to run the
149 * ready fibrils which are not serialized.
150 */
151 if ((list_empty(&serialized_list)) &&
152 (threads_in_manager <= serialized_threads)) {
153 goto ret_0;
154 }
155 }
156
157 /* If we are going to manager and none exists, create it */
158 if ((stype == FIBRIL_TO_MANAGER) || (stype == FIBRIL_FROM_DEAD)) {
159 while (list_empty(&manager_list)) {
160 futex_up(&fibril_futex);
161 async_create_manager();
162 futex_down(&fibril_futex);
163 }
164 }
165
166 fibril_t *srcf = __tcb_get()->fibril_data;
167 if (stype != FIBRIL_FROM_DEAD) {
168
169 /* Save current state */
170 if (!context_save(&srcf->ctx)) {
171 if (serialization_count)
172 srcf->flags &= ~FIBRIL_SERIALIZED;
173
174 if (srcf->clean_after_me) {
175 /*
176 * Cleanup after the dead fibril from which we
177 * restored context here.
178 */
179 void *stack = srcf->clean_after_me->stack;
180 if (stack) {
181 /*
182 * This check is necessary because a
183 * thread could have exited like a
184 * normal fibril using the
185 * FIBRIL_FROM_DEAD switch type. In that
186 * case, its fibril will not have the
187 * stack member filled.
188 */
189 free(stack);
190 }
191 fibril_teardown(srcf->clean_after_me);
192 srcf->clean_after_me = NULL;
193 }
194
195 return 1; /* futex_up already done here */
196 }
197
198 /* Save myself to the correct run list */
199 if (stype == FIBRIL_PREEMPT)
200 list_append(&srcf->link, &ready_list);
201 else if (stype == FIBRIL_FROM_MANAGER) {
202 list_append(&srcf->link, &manager_list);
203 threads_in_manager--;
204 } else {
205 /*
206 * If stype == FIBRIL_TO_MANAGER, don't put ourselves to
207 * any list, we should already be somewhere, or we will
208 * be lost.
209 */
210 }
211 }
212
213 /* Choose a new fibril to run */
214 fibril_t *dstf;
215 if ((stype == FIBRIL_TO_MANAGER) || (stype == FIBRIL_FROM_DEAD)) {
216 dstf = list_get_instance(manager_list.next, fibril_t, link);
217 if (serialization_count && stype == FIBRIL_TO_MANAGER) {
218 serialized_threads++;
219 srcf->flags |= FIBRIL_SERIALIZED;
220 }
221 threads_in_manager++;
222
223 if (stype == FIBRIL_FROM_DEAD)
224 dstf->clean_after_me = srcf;
225 } else {
226 if (!list_empty(&serialized_list)) {
227 dstf = list_get_instance(serialized_list.next, fibril_t,
228 link);
229 serialized_threads--;
230 } else {
231 dstf = list_get_instance(ready_list.next, fibril_t,
232 link);
233 }
234 }
235 list_remove(&dstf->link);
236
237 futex_up(&fibril_futex);
238 context_restore(&dstf->ctx);
239 /* not reached */
240
241ret_0:
242 futex_up(&fibril_futex);
243 return retval;
244}
245
246/** Create a new fibril.
247 *
248 * @param func Implementing function of the new fibril.
249 * @param arg Argument to pass to func.
250 *
251 * @return Return 0 on failure or TLS of the new fibril.
252 */
253fid_t fibril_create(int (*func)(void *), void *arg)
254{
255 fibril_t *f;
256
257 f = fibril_setup();
258 if (!f)
259 return 0;
260 f->stack = (char *) malloc(FIBRIL_INITIAL_STACK_PAGES_NO *
261 getpagesize());
262 if (!f->stack) {
263 fibril_teardown(f);
264 return 0;
265 }
266
267 f->func = func;
268 f->arg = arg;
269
270 context_save(&f->ctx);
271 context_set(&f->ctx, FADDR(fibril_main), f->stack,
272 FIBRIL_INITIAL_STACK_PAGES_NO * getpagesize(), f->tcb);
273
274 return (fid_t) f;
275}
276
277/** Add a fibril to the ready list.
278 *
279 * @param fid Pointer to the fibril structure of the fibril to be
280 * added.
281 */
282void fibril_add_ready(fid_t fid)
283{
284 fibril_t *f;
285
286 f = (fibril_t *) fid;
287 futex_down(&fibril_futex);
288 if ((f->flags & FIBRIL_SERIALIZED))
289 list_append(&f->link, &serialized_list);
290 else
291 list_append(&f->link, &ready_list);
292 futex_up(&fibril_futex);
293}
294
295/** Add a fibril to the manager list.
296 *
297 * @param fid Pointer to the fibril structure of the fibril to be
298 * added.
299 */
300void fibril_add_manager(fid_t fid)
301{
302 fibril_t *f;
303
304 f = (fibril_t *) fid;
305
306 futex_down(&fibril_futex);
307 list_append(&f->link, &manager_list);
308 futex_up(&fibril_futex);
309}
310
311/** Remove one manager from the manager list. */
312void fibril_remove_manager(void)
313{
314 futex_down(&fibril_futex);
315 if (list_empty(&manager_list)) {
316 futex_up(&fibril_futex);
317 return;
318 }
319 list_remove(manager_list.next);
320 futex_up(&fibril_futex);
321}
322
323/** Return fibril id of the currently running fibril.
324 *
325 * @return fibril ID of the currently running fibril.
326 *
327 */
328fid_t fibril_get_id(void)
329{
330 return (fid_t) __tcb_get()->fibril_data;
331}
332
333/** Disable preemption
334 *
335 * If the fibril wants to send several message in a row and does not want to be
336 * preempted, it should start async_serialize_start() in the beginning of
337 * communication and async_serialize_end() in the end. If it is a true
338 * multithreaded application, it should protect the communication channel by a
339 * futex as well.
340 *
341 */
342void fibril_inc_sercount(void)
343{
344 serialization_count++;
345}
346
347/** Restore the preemption counter to the previous state. */
348void fibril_dec_sercount(void)
349{
350 serialization_count--;
351}
352
353/** @}
354 */
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