xref: /freebsd/contrib/ntp/sntp/libevent/evthread.c (revision c66ec88fed842fbaad62c30d510644ceb7bd2d71) 
1 /*
2  * Copyright (c) 2008-2012 Niels Provos, Nick Mathewson
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  * 1. Redistributions of source code must retain the above copyright
8  *    notice, this list of conditions and the following disclaimer.
9  * 2. Redistributions in binary form must reproduce the above copyright
10  *    notice, this list of conditions and the following disclaimer in the
11  *    documentation and/or other materials provided with the distribution.
12  * 3. The name of the author may not be used to endorse or promote products
13  *    derived from this software without specific prior written permission.
14  *
15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25  */
26 
27 #include "event2/event-config.h"
28 #include "evconfig-private.h"
29 
30 #ifndef EVENT__DISABLE_THREAD_SUPPORT
31 
32 #include "event2/thread.h"
33 
34 #include <stdlib.h>
35 #include <string.h>
36 
37 #include "log-internal.h"
38 #include "mm-internal.h"
39 #include "util-internal.h"
40 #include "evthread-internal.h"
41 
42 #ifdef EVTHREAD_EXPOSE_STRUCTS
43 #define GLOBAL
44 #else
45 #define GLOBAL static
46 #endif
47 
48 /* globals */
49 GLOBAL int evthread_lock_debugging_enabled_ = 0;
50 GLOBAL struct evthread_lock_callbacks evthread_lock_fns_ = {
51 	0, 0, NULL, NULL, NULL, NULL
52 };
53 GLOBAL unsigned long (*evthread_id_fn_)(void) = NULL;
54 GLOBAL struct evthread_condition_callbacks evthread_cond_fns_ = {
55 	0, NULL, NULL, NULL, NULL
56 };
57 
58 /* Used for debugging */
59 static struct evthread_lock_callbacks original_lock_fns_ = {
60 	0, 0, NULL, NULL, NULL, NULL
61 };
62 static struct evthread_condition_callbacks original_cond_fns_ = {
63 	0, NULL, NULL, NULL, NULL
64 };
65 
66 void
67 evthread_set_id_callback(unsigned long (*id_fn)(void))
68 {
69 	evthread_id_fn_ = id_fn;
70 }
71 
72 struct evthread_lock_callbacks *evthread_get_lock_callbacks()
73 {
74 	return evthread_lock_debugging_enabled_
75 	    ? &original_lock_fns_ : &evthread_lock_fns_;
76 }
77 struct evthread_condition_callbacks *evthread_get_condition_callbacks()
78 {
79 	return evthread_lock_debugging_enabled_
80 	    ? &original_cond_fns_ : &evthread_cond_fns_;
81 }
82 void evthreadimpl_disable_lock_debugging_(void)
83 {
84 	evthread_lock_debugging_enabled_ = 0;
85 }
86 
87 int
88 evthread_set_lock_callbacks(const struct evthread_lock_callbacks *cbs)
89 {
90 	struct evthread_lock_callbacks *target = evthread_get_lock_callbacks();
91 
92 	if (!cbs) {
93 		if (target->alloc)
94 			event_warnx("Trying to disable lock functions after "
95 			    "they have been set up will probaby not work.");
96 		memset(target, 0, sizeof(evthread_lock_fns_));
97 		return 0;
98 	}
99 	if (target->alloc) {
100 		/* Uh oh; we already had locking callbacks set up.*/
101 		if (target->lock_api_version == cbs->lock_api_version &&
102 			target->supported_locktypes == cbs->supported_locktypes &&
103 			target->alloc == cbs->alloc &&
104 			target->free == cbs->free &&
105 			target->lock == cbs->lock &&
106 			target->unlock == cbs->unlock) {
107 			/* no change -- allow this. */
108 			return 0;
109 		}
110 		event_warnx("Can't change lock callbacks once they have been "
111 		    "initialized.");
112 		return -1;
113 	}
114 	if (cbs->alloc && cbs->free && cbs->lock && cbs->unlock) {
115 		memcpy(target, cbs, sizeof(evthread_lock_fns_));
116 		return event_global_setup_locks_(1);
117 	} else {
118 		return -1;
119 	}
120 }
121 
122 int
123 evthread_set_condition_callbacks(const struct evthread_condition_callbacks *cbs)
124 {
125 	struct evthread_condition_callbacks *target = evthread_get_condition_callbacks();
126 
127 	if (!cbs) {
128 		if (target->alloc_condition)
129 			event_warnx("Trying to disable condition functions "
130 			    "after they have been set up will probaby not "
131 			    "work.");
132 		memset(target, 0, sizeof(evthread_cond_fns_));
133 		return 0;
134 	}
135 	if (target->alloc_condition) {
136 		/* Uh oh; we already had condition callbacks set up.*/
137 		if (target->condition_api_version == cbs->condition_api_version &&
138 			target->alloc_condition == cbs->alloc_condition &&
139 			target->free_condition == cbs->free_condition &&
140 			target->signal_condition == cbs->signal_condition &&
141 			target->wait_condition == cbs->wait_condition) {
142 			/* no change -- allow this. */
143 			return 0;
144 		}
145 		event_warnx("Can't change condition callbacks once they "
146 		    "have been initialized.");
147 		return -1;
148 	}
149 	if (cbs->alloc_condition && cbs->free_condition &&
150 	    cbs->signal_condition && cbs->wait_condition) {
151 		memcpy(target, cbs, sizeof(evthread_cond_fns_));
152 	}
153 	if (evthread_lock_debugging_enabled_) {
154 		evthread_cond_fns_.alloc_condition = cbs->alloc_condition;
155 		evthread_cond_fns_.free_condition = cbs->free_condition;
156 		evthread_cond_fns_.signal_condition = cbs->signal_condition;
157 	}
158 	return 0;
159 }
160 
161 #define DEBUG_LOCK_SIG	0xdeb0b10c
162 
163 struct debug_lock {
164 	unsigned signature;
165 	unsigned locktype;
166 	unsigned long held_by;
167 	/* XXXX if we ever use read-write locks, we will need a separate
168 	 * lock to protect count. */
169 	int count;
170 	void *lock;
171 };
172 
173 static void *
174 debug_lock_alloc(unsigned locktype)
175 {
176 	struct debug_lock *result = mm_malloc(sizeof(struct debug_lock));
177 	if (!result)
178 		return NULL;
179 	if (original_lock_fns_.alloc) {
180 		if (!(result->lock = original_lock_fns_.alloc(
181 				locktype|EVTHREAD_LOCKTYPE_RECURSIVE))) {
182 			mm_free(result);
183 			return NULL;
184 		}
185 	} else {
186 		result->lock = NULL;
187 	}
188 	result->signature = DEBUG_LOCK_SIG;
189 	result->locktype = locktype;
190 	result->count = 0;
191 	result->held_by = 0;
192 	return result;
193 }
194 
195 static void
196 debug_lock_free(void *lock_, unsigned locktype)
197 {
198 	struct debug_lock *lock = lock_;
199 	EVUTIL_ASSERT(lock->count == 0);
200 	EVUTIL_ASSERT(locktype == lock->locktype);
201 	EVUTIL_ASSERT(DEBUG_LOCK_SIG == lock->signature);
202 	if (original_lock_fns_.free) {
203 		original_lock_fns_.free(lock->lock,
204 		    lock->locktype|EVTHREAD_LOCKTYPE_RECURSIVE);
205 	}
206 	lock->lock = NULL;
207 	lock->count = -100;
208 	lock->signature = 0x12300fda;
209 	mm_free(lock);
210 }
211 
212 static void
213 evthread_debug_lock_mark_locked(unsigned mode, struct debug_lock *lock)
214 {
215 	EVUTIL_ASSERT(DEBUG_LOCK_SIG == lock->signature);
216 	++lock->count;
217 	if (!(lock->locktype & EVTHREAD_LOCKTYPE_RECURSIVE))
218 		EVUTIL_ASSERT(lock->count == 1);
219 	if (evthread_id_fn_) {
220 		unsigned long me;
221 		me = evthread_id_fn_();
222 		if (lock->count > 1)
223 			EVUTIL_ASSERT(lock->held_by == me);
224 		lock->held_by = me;
225 	}
226 }
227 
228 static int
229 debug_lock_lock(unsigned mode, void *lock_)
230 {
231 	struct debug_lock *lock = lock_;
232 	int res = 0;
233 	if (lock->locktype & EVTHREAD_LOCKTYPE_READWRITE)
234 		EVUTIL_ASSERT(mode & (EVTHREAD_READ|EVTHREAD_WRITE));
235 	else
236 		EVUTIL_ASSERT((mode & (EVTHREAD_READ|EVTHREAD_WRITE)) == 0);
237 	if (original_lock_fns_.lock)
238 		res = original_lock_fns_.lock(mode, lock->lock);
239 	if (!res) {
240 		evthread_debug_lock_mark_locked(mode, lock);
241 	}
242 	return res;
243 }
244 
245 static void
246 evthread_debug_lock_mark_unlocked(unsigned mode, struct debug_lock *lock)
247 {
248 	EVUTIL_ASSERT(DEBUG_LOCK_SIG == lock->signature);
249 	if (lock->locktype & EVTHREAD_LOCKTYPE_READWRITE)
250 		EVUTIL_ASSERT(mode & (EVTHREAD_READ|EVTHREAD_WRITE));
251 	else
252 		EVUTIL_ASSERT((mode & (EVTHREAD_READ|EVTHREAD_WRITE)) == 0);
253 	if (evthread_id_fn_) {
254 		unsigned long me;
255 		me = evthread_id_fn_();
256 		EVUTIL_ASSERT(lock->held_by == me);
257 		if (lock->count == 1)
258 			lock->held_by = 0;
259 	}
260 	--lock->count;
261 	EVUTIL_ASSERT(lock->count >= 0);
262 }
263 
264 static int
265 debug_lock_unlock(unsigned mode, void *lock_)
266 {
267 	struct debug_lock *lock = lock_;
268 	int res = 0;
269 	evthread_debug_lock_mark_unlocked(mode, lock);
270 	if (original_lock_fns_.unlock)
271 		res = original_lock_fns_.unlock(mode, lock->lock);
272 	return res;
273 }
274 
275 static int
276 debug_cond_wait(void *cond_, void *lock_, const struct timeval *tv)
277 {
278 	int r;
279 	struct debug_lock *lock = lock_;
280 	EVUTIL_ASSERT(lock);
281 	EVUTIL_ASSERT(DEBUG_LOCK_SIG == lock->signature);
282 	EVLOCK_ASSERT_LOCKED(lock_);
283 	evthread_debug_lock_mark_unlocked(0, lock);
284 	r = original_cond_fns_.wait_condition(cond_, lock->lock, tv);
285 	evthread_debug_lock_mark_locked(0, lock);
286 	return r;
287 }
288 
289 /* misspelled version for backward compatibility */
290 void
291 evthread_enable_lock_debuging(void)
292 {
293 	evthread_enable_lock_debugging();
294 }
295 
296 void
297 evthread_enable_lock_debugging(void)
298 {
299 	struct evthread_lock_callbacks cbs = {
300 		EVTHREAD_LOCK_API_VERSION,
301 		EVTHREAD_LOCKTYPE_RECURSIVE,
302 		debug_lock_alloc,
303 		debug_lock_free,
304 		debug_lock_lock,
305 		debug_lock_unlock
306 	};
307 	if (evthread_lock_debugging_enabled_)
308 		return;
309 	memcpy(&original_lock_fns_, &evthread_lock_fns_,
310 	    sizeof(struct evthread_lock_callbacks));
311 	memcpy(&evthread_lock_fns_, &cbs,
312 	    sizeof(struct evthread_lock_callbacks));
313 
314 	memcpy(&original_cond_fns_, &evthread_cond_fns_,
315 	    sizeof(struct evthread_condition_callbacks));
316 	evthread_cond_fns_.wait_condition = debug_cond_wait;
317 	evthread_lock_debugging_enabled_ = 1;
318 
319 	/* XXX return value should get checked. */
320 	event_global_setup_locks_(0);
321 }
322 
323 int
324 evthread_is_debug_lock_held_(void *lock_)
325 {
326 	struct debug_lock *lock = lock_;
327 	if (! lock->count)
328 		return 0;
329 	if (evthread_id_fn_) {
330 		unsigned long me = evthread_id_fn_();
331 		if (lock->held_by != me)
332 			return 0;
333 	}
334 	return 1;
335 }
336 
337 void *
338 evthread_debug_get_real_lock_(void *lock_)
339 {
340 	struct debug_lock *lock = lock_;
341 	return lock->lock;
342 }
343 
344 void *
345 evthread_setup_global_lock_(void *lock_, unsigned locktype, int enable_locks)
346 {
347 	/* there are four cases here:
348 	   1) we're turning on debugging; locking is not on.
349 	   2) we're turning on debugging; locking is on.
350 	   3) we're turning on locking; debugging is not on.
351 	   4) we're turning on locking; debugging is on. */
352 
353 	if (!enable_locks && original_lock_fns_.alloc == NULL) {
354 		/* Case 1: allocate a debug lock. */
355 		EVUTIL_ASSERT(lock_ == NULL);
356 		return debug_lock_alloc(locktype);
357 	} else if (!enable_locks && original_lock_fns_.alloc != NULL) {
358 		/* Case 2: wrap the lock in a debug lock. */
359 		struct debug_lock *lock;
360 		EVUTIL_ASSERT(lock_ != NULL);
361 
362 		if (!(locktype & EVTHREAD_LOCKTYPE_RECURSIVE)) {
363 			/* We can't wrap it: We need a recursive lock */
364 			original_lock_fns_.free(lock_, locktype);
365 			return debug_lock_alloc(locktype);
366 		}
367 		lock = mm_malloc(sizeof(struct debug_lock));
368 		if (!lock) {
369 			original_lock_fns_.free(lock_, locktype);
370 			return NULL;
371 		}
372 		lock->lock = lock_;
373 		lock->locktype = locktype;
374 		lock->count = 0;
375 		lock->held_by = 0;
376 		return lock;
377 	} else if (enable_locks && ! evthread_lock_debugging_enabled_) {
378 		/* Case 3: allocate a regular lock */
379 		EVUTIL_ASSERT(lock_ == NULL);
380 		return evthread_lock_fns_.alloc(locktype);
381 	} else {
382 		/* Case 4: Fill in a debug lock with a real lock */
383 		struct debug_lock *lock = lock_;
384 		EVUTIL_ASSERT(enable_locks &&
385 		              evthread_lock_debugging_enabled_);
386 		EVUTIL_ASSERT(lock->locktype == locktype);
387 		EVUTIL_ASSERT(lock->lock == NULL);
388 		lock->lock = original_lock_fns_.alloc(
389 			locktype|EVTHREAD_LOCKTYPE_RECURSIVE);
390 		if (!lock->lock) {
391 			lock->count = -200;
392 			mm_free(lock);
393 			return NULL;
394 		}
395 		return lock;
396 	}
397 }
398 
399 
400 #ifndef EVTHREAD_EXPOSE_STRUCTS
401 unsigned long
402 evthreadimpl_get_id_()
403 {
404 	return evthread_id_fn_ ? evthread_id_fn_() : 1;
405 }
406 void *
407 evthreadimpl_lock_alloc_(unsigned locktype)
408 {
409 	return evthread_lock_fns_.alloc ?
410 	    evthread_lock_fns_.alloc(locktype) : NULL;
411 }
412 void
413 evthreadimpl_lock_free_(void *lock, unsigned locktype)
414 {
415 	if (evthread_lock_fns_.free)
416 		evthread_lock_fns_.free(lock, locktype);
417 }
418 int
419 evthreadimpl_lock_lock_(unsigned mode, void *lock)
420 {
421 	if (evthread_lock_fns_.lock)
422 		return evthread_lock_fns_.lock(mode, lock);
423 	else
424 		return 0;
425 }
426 int
427 evthreadimpl_lock_unlock_(unsigned mode, void *lock)
428 {
429 	if (evthread_lock_fns_.unlock)
430 		return evthread_lock_fns_.unlock(mode, lock);
431 	else
432 		return 0;
433 }
434 void *
435 evthreadimpl_cond_alloc_(unsigned condtype)
436 {
437 	return evthread_cond_fns_.alloc_condition ?
438 	    evthread_cond_fns_.alloc_condition(condtype) : NULL;
439 }
440 void
441 evthreadimpl_cond_free_(void *cond)
442 {
443 	if (evthread_cond_fns_.free_condition)
444 		evthread_cond_fns_.free_condition(cond);
445 }
446 int
447 evthreadimpl_cond_signal_(void *cond, int broadcast)
448 {
449 	if (evthread_cond_fns_.signal_condition)
450 		return evthread_cond_fns_.signal_condition(cond, broadcast);
451 	else
452 		return 0;
453 }
454 int
455 evthreadimpl_cond_wait_(void *cond, void *lock, const struct timeval *tv)
456 {
457 	if (evthread_cond_fns_.wait_condition)
458 		return evthread_cond_fns_.wait_condition(cond, lock, tv);
459 	else
460 		return 0;
461 }
462 int
463 evthreadimpl_is_lock_debugging_enabled_(void)
464 {
465 	return evthread_lock_debugging_enabled_;
466 }
467 
468 int
469 evthreadimpl_locking_enabled_(void)
470 {
471 	return evthread_lock_fns_.lock != NULL;
472 }
473 #endif
474 
475 #endif
476