xref: /freebsd/lib/libthr/thread/thr_list.c (revision 1e413cf93298b5b97441a21d9a50fdcd0ee9945e)
1 /*
2  * Copyright (c) 2005 David Xu <davidxu@freebsd.org>
3  * Copyright (C) 2003 Daniel M. Eischen <deischen@freebsd.org>
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  * 1. Redistributions of source code must retain the above copyright
10  *    notice unmodified, this list of conditions, and the following
11  *    disclaimer.
12  * 2. 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  *
16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26  *
27  * $FreeBSD$
28  */
29 
30 #include <sys/types.h>
31 #include <sys/queue.h>
32 
33 #include <stdlib.h>
34 #include <string.h>
35 #include <pthread.h>
36 
37 #include "thr_private.h"
38 #include "libc_private.h"
39 
40 /*#define DEBUG_THREAD_LIST */
41 #ifdef DEBUG_THREAD_LIST
42 #define DBG_MSG		stdout_debug
43 #else
44 #define DBG_MSG(x...)
45 #endif
46 
47 #define MAX_THREADS		100000
48 
49 /*
50  * Define a high water mark for the maximum number of threads that
51  * will be cached.  Once this level is reached, any extra threads
52  * will be free()'d.
53  */
54 #define	MAX_CACHED_THREADS	100
55 
56 /*
57  * We've got to keep track of everything that is allocated, not only
58  * to have a speedy free list, but also so they can be deallocated
59  * after a fork().
60  */
61 static TAILQ_HEAD(, pthread)	free_threadq;
62 static struct umutex		free_thread_lock = DEFAULT_UMUTEX;
63 static struct umutex		tcb_lock = DEFAULT_UMUTEX;
64 static int			free_thread_count = 0;
65 static int			inited = 0;
66 static int			total_threads;
67 
68 LIST_HEAD(thread_hash_head, pthread);
69 #define HASH_QUEUES	128
70 static struct thread_hash_head	thr_hashtable[HASH_QUEUES];
71 #define	THREAD_HASH(thrd)	(((unsigned long)thrd >> 8) % HASH_QUEUES)
72 
73 static void thr_destroy(struct pthread *curthread, struct pthread *thread);
74 
75 void
76 _thr_list_init(void)
77 {
78 	int i;
79 
80 	_gc_count = 0;
81 	total_threads = 1;
82 	_thr_umutex_init(&_thr_list_lock);
83 	TAILQ_INIT(&_thread_list);
84 	TAILQ_INIT(&free_threadq);
85 	_thr_umutex_init(&free_thread_lock);
86 	_thr_umutex_init(&tcb_lock);
87 	if (inited) {
88 		for (i = 0; i < HASH_QUEUES; ++i)
89 			LIST_INIT(&thr_hashtable[i]);
90 	}
91 	inited = 1;
92 }
93 
94 void
95 _thr_gc(struct pthread *curthread)
96 {
97 	struct pthread *td, *td_next;
98 	TAILQ_HEAD(, pthread) worklist;
99 
100 	TAILQ_INIT(&worklist);
101 	THREAD_LIST_LOCK(curthread);
102 
103 	/* Check the threads waiting for GC. */
104 	TAILQ_FOREACH_SAFE(td, &_thread_gc_list, gcle, td_next) {
105 		if (td->tid != TID_TERMINATED) {
106 			/* make sure we are not still in userland */
107 			continue;
108 		}
109 		_thr_stack_free(&td->attr);
110 		if (((td->tlflags & TLFLAGS_DETACHED) != 0) &&
111 		    (td->refcount == 0)) {
112 			THR_GCLIST_REMOVE(td);
113 			/*
114 			 * The thread has detached and is no longer
115 			 * referenced.  It is safe to remove all
116 			 * remnants of the thread.
117 			 */
118 			THR_LIST_REMOVE(td);
119 			TAILQ_INSERT_HEAD(&worklist, td, gcle);
120 		}
121 	}
122 	THREAD_LIST_UNLOCK(curthread);
123 
124 	while ((td = TAILQ_FIRST(&worklist)) != NULL) {
125 		TAILQ_REMOVE(&worklist, td, gcle);
126 		/*
127 		 * XXX we don't free initial thread, because there might
128 		 * have some code referencing initial thread.
129 		 */
130 		if (td == _thr_initial) {
131 			DBG_MSG("Initial thread won't be freed\n");
132 			continue;
133 		}
134 
135 		_thr_free(curthread, td);
136 	}
137 }
138 
139 struct pthread *
140 _thr_alloc(struct pthread *curthread)
141 {
142 	struct pthread	*thread = NULL;
143 	struct tcb	*tcb;
144 
145 	if (curthread != NULL) {
146 		if (GC_NEEDED())
147 			_thr_gc(curthread);
148 		if (free_thread_count > 0) {
149 			THR_LOCK_ACQUIRE(curthread, &free_thread_lock);
150 			if ((thread = TAILQ_FIRST(&free_threadq)) != NULL) {
151 				TAILQ_REMOVE(&free_threadq, thread, tle);
152 				free_thread_count--;
153 			}
154 			THR_LOCK_RELEASE(curthread, &free_thread_lock);
155 		}
156 	}
157 	if (thread == NULL) {
158 		if (total_threads > MAX_THREADS)
159 			return (NULL);
160 		atomic_fetchadd_int(&total_threads, 1);
161 		thread = malloc(sizeof(struct pthread));
162 		if (thread == NULL) {
163 			atomic_fetchadd_int(&total_threads, -1);
164 			return (NULL);
165 		}
166 	}
167 	if (curthread != NULL) {
168 		THR_LOCK_ACQUIRE(curthread, &tcb_lock);
169 		tcb = _tcb_ctor(thread, 0 /* not initial tls */);
170 		THR_LOCK_RELEASE(curthread, &tcb_lock);
171 	} else {
172 		tcb = _tcb_ctor(thread, 1 /* initial tls */);
173 	}
174 	if (tcb != NULL) {
175 		memset(thread, 0, sizeof(*thread));
176 		thread->tcb = tcb;
177 	} else {
178 		thr_destroy(curthread, thread);
179 		atomic_fetchadd_int(&total_threads, -1);
180 		thread = NULL;
181 	}
182 	return (thread);
183 }
184 
185 void
186 _thr_free(struct pthread *curthread, struct pthread *thread)
187 {
188 	DBG_MSG("Freeing thread %p\n", thread);
189 
190 	/*
191 	 * Always free tcb, as we only know it is part of RTLD TLS
192 	 * block, but don't know its detail and can not assume how
193 	 * it works, so better to avoid caching it here.
194 	 */
195 	if (curthread != NULL) {
196 		THR_LOCK_ACQUIRE(curthread, &tcb_lock);
197 		_tcb_dtor(thread->tcb);
198 		THR_LOCK_RELEASE(curthread, &tcb_lock);
199 	} else {
200 		_tcb_dtor(thread->tcb);
201 	}
202 	thread->tcb = NULL;
203 	if ((curthread == NULL) || (free_thread_count >= MAX_CACHED_THREADS)) {
204 		thr_destroy(curthread, thread);
205 		atomic_fetchadd_int(&total_threads, -1);
206 	} else {
207 		/*
208 		 * Add the thread to the free thread list, this also avoids
209 		 * pthread id is reused too quickly, may help some buggy apps.
210 		 */
211 		THR_LOCK_ACQUIRE(curthread, &free_thread_lock);
212 		TAILQ_INSERT_TAIL(&free_threadq, thread, tle);
213 		free_thread_count++;
214 		THR_LOCK_RELEASE(curthread, &free_thread_lock);
215 	}
216 }
217 
218 static void
219 thr_destroy(struct pthread *curthread __unused, struct pthread *thread)
220 {
221 	free(thread);
222 }
223 
224 /*
225  * Add the thread to the list of all threads and increment
226  * number of active threads.
227  */
228 void
229 _thr_link(struct pthread *curthread, struct pthread *thread)
230 {
231 	THREAD_LIST_LOCK(curthread);
232 	THR_LIST_ADD(thread);
233 	_thread_active_threads++;
234 	THREAD_LIST_UNLOCK(curthread);
235 }
236 
237 /*
238  * Remove an active thread.
239  */
240 void
241 _thr_unlink(struct pthread *curthread, struct pthread *thread)
242 {
243 	THREAD_LIST_LOCK(curthread);
244 	THR_LIST_REMOVE(thread);
245 	_thread_active_threads--;
246 	THREAD_LIST_UNLOCK(curthread);
247 }
248 
249 void
250 _thr_hash_add(struct pthread *thread)
251 {
252 	struct thread_hash_head *head;
253 
254 	head = &thr_hashtable[THREAD_HASH(thread)];
255 	LIST_INSERT_HEAD(head, thread, hle);
256 }
257 
258 void
259 _thr_hash_remove(struct pthread *thread)
260 {
261 	LIST_REMOVE(thread, hle);
262 }
263 
264 struct pthread *
265 _thr_hash_find(struct pthread *thread)
266 {
267 	struct pthread *td;
268 	struct thread_hash_head *head;
269 
270 	head = &thr_hashtable[THREAD_HASH(thread)];
271 	LIST_FOREACH(td, head, hle) {
272 		if (td == thread)
273 			return (thread);
274 	}
275 	return (NULL);
276 }
277 
278 /*
279  * Find a thread in the linked list of active threads and add a reference
280  * to it.  Threads with positive reference counts will not be deallocated
281  * until all references are released.
282  */
283 int
284 _thr_ref_add(struct pthread *curthread, struct pthread *thread,
285     int include_dead)
286 {
287 	int ret;
288 
289 	if (thread == NULL)
290 		/* Invalid thread: */
291 		return (EINVAL);
292 
293 	THREAD_LIST_LOCK(curthread);
294 	if ((ret = _thr_find_thread(curthread, thread, include_dead)) == 0) {
295 		thread->refcount++;
296 		THR_CRITICAL_ENTER(curthread);
297 	}
298 	THREAD_LIST_UNLOCK(curthread);
299 
300 	/* Return zero if the thread exists: */
301 	return (ret);
302 }
303 
304 void
305 _thr_ref_delete(struct pthread *curthread, struct pthread *thread)
306 {
307 	THREAD_LIST_LOCK(curthread);
308 	_thr_ref_delete_unlocked(curthread, thread);
309 	THREAD_LIST_UNLOCK(curthread);
310 }
311 
312 void
313 _thr_ref_delete_unlocked(struct pthread *curthread,
314 	struct pthread *thread)
315 {
316 	if (thread != NULL) {
317 		thread->refcount--;
318 		if ((thread->refcount == 0) && thread->state == PS_DEAD &&
319 		    (thread->tlflags & TLFLAGS_DETACHED) != 0)
320 			THR_GCLIST_ADD(thread);
321 		THR_CRITICAL_LEAVE(curthread);
322 	}
323 }
324 
325 int
326 _thr_find_thread(struct pthread *curthread __unused, struct pthread *thread,
327     int include_dead)
328 {
329 	struct pthread *pthread;
330 
331 	if (thread == NULL)
332 		/* Invalid thread: */
333 		return (EINVAL);
334 
335 	pthread = _thr_hash_find(thread);
336 	if (pthread) {
337 		if (include_dead == 0 && pthread->state == PS_DEAD) {
338 			pthread = NULL;
339 		}
340 	}
341 
342 	/* Return zero if the thread exists: */
343 	return ((pthread != NULL) ? 0 : ESRCH);
344 }
345