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  * $DragonFly: src/lib/libthread_xu/thread/thr_list.c,v 1.7 2006/04/06 13:03:09 davidxu Exp $
28  */
29 
30 #include <sys/cdefs.h>
31 #include <sys/types.h>
32 #include <sys/queue.h>
33 
34 #include <stdlib.h>
35 #include <string.h>
36 #include <pthread.h>
37 
38 #include "thr_private.h"
39 #include "libc_private.h"
40 
41 /* #define DEBUG_THREAD_LIST */
42 #ifdef DEBUG_THREAD_LIST
43 #define DBG_MSG		stdout_debug
44 #else
45 #define DBG_MSG(x...)
46 #endif
47 
48 /* List of all threads */
49 struct thread_head _thread_list = TAILQ_HEAD_INITIALIZER(_thread_list);
50 
51 /* List of threads needing GC */
52 struct thread_head _thread_gc_list = TAILQ_HEAD_INITIALIZER(_thread_gc_list);
53 
54 /* Number of active threads */
55 int	_thread_active_threads = 1;
56 
57 /* Garbage thread count. */
58 int	_thr_gc_count;
59 
60 umtx_t	_thr_list_lock;
61 
62 /*
63  * Define a high water mark for the maximum number of threads that
64  * will be cached.  Once this level is reached, any extra threads
65  * will be free()'d.
66  */
67 #define	MAX_CACHED_THREADS	100
68 
69 /*
70  * We've got to keep track of everything that is allocated, not only
71  * to have a speedy free list, but also so they can be deallocated
72  * after a fork().
73  */
74 static TAILQ_HEAD(, pthread)	free_threadq;
75 static umtx_t			free_thread_lock;
76 static umtx_t			tcb_lock;
77 static int			free_thread_count = 0;
78 static int			inited = 0;
79 static u_int64_t		next_uniqueid = 1;
80 
81 LIST_HEAD(thread_hash_head, pthread);
82 #define HASH_QUEUES	128
83 static struct thread_hash_head	thr_hashtable[HASH_QUEUES];
84 #define	THREAD_HASH(thrd)	(((unsigned long)thrd >> 12) % HASH_QUEUES)
85 
86 static void thr_destroy(struct pthread *curthread, struct pthread *thread);
87 
88 void
89 _thr_list_init(void)
90 {
91 	int i;
92 
93 	_thr_gc_count = 0;
94 	_thr_umtx_init(&_thr_list_lock);
95 	TAILQ_INIT(&_thread_list);
96 	TAILQ_INIT(&free_threadq);
97 	_thr_umtx_init(&free_thread_lock);
98 	_thr_umtx_init(&tcb_lock);
99 	if (inited) {
100 		for (i = 0; i < HASH_QUEUES; ++i)
101 			LIST_INIT(&thr_hashtable[i]);
102 	}
103 	inited = 1;
104 }
105 
106 void
107 _thr_gc(struct pthread *curthread)
108 {
109 	struct pthread *td, *td_next;
110 	TAILQ_HEAD(, pthread) worklist;
111 
112 	TAILQ_INIT(&worklist);
113 	THREAD_LIST_LOCK(curthread);
114 
115 	/* Check the threads waiting for GC. */
116 	for (td = TAILQ_FIRST(&_thread_gc_list); td != NULL; td = td_next) {
117 		td_next = TAILQ_NEXT(td, gcle);
118 		if (td->terminated == 0) {
119 			/* make sure we are not still in userland */
120 			continue;
121 		}
122 		_thr_stack_free(&td->attr);
123 		if (((td->tlflags & TLFLAGS_DETACHED) != 0) &&
124 		    (td->refcount == 0)) {
125 			THR_GCLIST_REMOVE(td);
126 			/*
127 			 * The thread has detached and is no longer
128 			 * referenced.  It is safe to remove all
129 			 * remnants of the thread.
130 			 */
131 			THR_LIST_REMOVE(td);
132 			TAILQ_INSERT_HEAD(&worklist, td, gcle);
133 		}
134 	}
135 	THREAD_LIST_UNLOCK(curthread);
136 
137 	while ((td = TAILQ_FIRST(&worklist)) != NULL) {
138 		TAILQ_REMOVE(&worklist, td, gcle);
139 		/*
140 		 * XXX we don't free initial thread, because there might
141 		 * have some code referencing initial thread.
142 		 */
143 		if (td == _thr_initial) {
144 			DBG_MSG("Initial thread won't be freed\n");
145 			continue;
146 		}
147 
148 		_thr_free(curthread, td);
149 	}
150 }
151 
152 struct pthread *
153 _thr_alloc(struct pthread *curthread)
154 {
155 	struct pthread	*thread = NULL;
156 	struct tls_tcb	*tcb;
157 
158 	if (curthread != NULL) {
159 		if (GC_NEEDED())
160 			_thr_gc(curthread);
161 		if (free_thread_count > 0) {
162 			THR_LOCK_ACQUIRE(curthread, &free_thread_lock);
163 			if ((thread = TAILQ_FIRST(&free_threadq)) != NULL) {
164 				TAILQ_REMOVE(&free_threadq, thread, tle);
165 				free_thread_count--;
166 			}
167 			THR_LOCK_RELEASE(curthread, &free_thread_lock);
168 		}
169 	}
170 	if (thread == NULL) {
171 		thread = malloc(sizeof(struct pthread));
172 		if (thread == NULL)
173 			return (NULL);
174 	}
175 	if (curthread != NULL) {
176 		THR_LOCK_ACQUIRE(curthread, &tcb_lock);
177 		tcb = _tcb_ctor(thread, 0 /* not initial tls */);
178 		THR_LOCK_RELEASE(curthread, &tcb_lock);
179 	} else {
180 		tcb = _tcb_ctor(thread, 1 /* initial tls */);
181 	}
182 	if (tcb != NULL) {
183 		memset(thread, 0, sizeof(*thread));
184 		thread->tcb = tcb;
185 	} else {
186 		thr_destroy(curthread, thread);
187 		thread = NULL;
188 	}
189 	return (thread);
190 }
191 
192 void
193 _thr_free(struct pthread *curthread, struct pthread *thread)
194 {
195 	DBG_MSG("Freeing thread %p\n", thread);
196 	if (thread->name) {
197 		free(thread->name);
198 		thread->name = NULL;
199 	}
200 	/*
201 	 * Always free tcb, as we only know it is part of RTLD TLS
202 	 * block, but don't know its detail and can not assume how
203 	 * it works, so better to avoid caching it here.
204 	 */
205 	if (curthread != NULL) {
206 		THR_LOCK_ACQUIRE(curthread, &tcb_lock);
207 		_tcb_dtor(thread->tcb);
208 		THR_LOCK_RELEASE(curthread, &tcb_lock);
209 	} else {
210 		_tcb_dtor(thread->tcb);
211 	}
212 	thread->tcb = NULL;
213 	if ((curthread == NULL) || (free_thread_count >= MAX_CACHED_THREADS)) {
214 		thr_destroy(curthread, thread);
215 	} else {
216 		/*
217 		 * Add the thread to the free thread list, this also avoids
218 		 * pthread id is reused too quickly, may help some buggy apps.
219 		 */
220 		THR_LOCK_ACQUIRE(curthread, &free_thread_lock);
221 		TAILQ_INSERT_TAIL(&free_threadq, thread, tle);
222 		free_thread_count++;
223 		THR_LOCK_RELEASE(curthread, &free_thread_lock);
224 	}
225 }
226 
227 static void
228 thr_destroy(struct pthread *curthread __unused, struct pthread *thread)
229 {
230 	free(thread);
231 }
232 
233 /*
234  * Add an active thread:
235  *
236  *   o Assign the thread a unique id (which GDB uses to track
237  *     threads.
238  *   o Add the thread to the list of all threads and increment
239  *     number of active threads.
240  */
241 void
242 _thr_link(struct pthread *curthread, struct pthread *thread)
243 {
244 	THREAD_LIST_LOCK(curthread);
245 	/*
246 	 * Initialize the unique id (which GDB uses to track
247 	 * threads), add the thread to the list of all threads,
248 	 * and
249 	 */
250 	thread->uniqueid = next_uniqueid++;
251 	THR_LIST_ADD(thread);
252 	_thread_active_threads++;
253 	THREAD_LIST_UNLOCK(curthread);
254 }
255 
256 /*
257  * Remove an active thread.
258  */
259 void
260 _thr_unlink(struct pthread *curthread, struct pthread *thread)
261 {
262 	THREAD_LIST_LOCK(curthread);
263 	THR_LIST_REMOVE(thread);
264 	_thread_active_threads--;
265 	THREAD_LIST_UNLOCK(curthread);
266 }
267 
268 void
269 _thr_hash_add(struct pthread *thread)
270 {
271 	struct thread_hash_head *head;
272 
273 	head = &thr_hashtable[THREAD_HASH(thread)];
274 	LIST_INSERT_HEAD(head, thread, hle);
275 }
276 
277 void
278 _thr_hash_remove(struct pthread *thread)
279 {
280 	LIST_REMOVE(thread, hle);
281 }
282 
283 struct pthread *
284 _thr_hash_find(struct pthread *thread)
285 {
286 	struct pthread *td;
287 	struct thread_hash_head *head;
288 
289 	head = &thr_hashtable[THREAD_HASH(thread)];
290 	LIST_FOREACH(td, head, hle) {
291 		if (td == thread)
292 			return (thread);
293 	}
294 	return (NULL);
295 }
296 
297 /*
298  * Find a thread in the linked list of active threads and add a reference
299  * to it.  Threads with positive reference counts will not be deallocated
300  * until all references are released.
301  */
302 int
303 _thr_ref_add(struct pthread *curthread, struct pthread *thread,
304     int include_dead)
305 {
306 	int ret;
307 
308 	if (thread == NULL)
309 		/* Invalid thread: */
310 		return (EINVAL);
311 
312 	THREAD_LIST_LOCK(curthread);
313 	if ((ret = _thr_find_thread(curthread, thread, include_dead)) == 0) {
314 		thread->refcount++;
315 	}
316 	THREAD_LIST_UNLOCK(curthread);
317 
318 	/* Return zero if the thread exists: */
319 	return (ret);
320 }
321 
322 void
323 _thr_ref_delete(struct pthread *curthread, struct pthread *thread)
324 {
325 	THREAD_LIST_LOCK(curthread);
326 	_thr_ref_delete_unlocked(curthread, thread);
327 	THREAD_LIST_UNLOCK(curthread);
328 }
329 
330 void
331 _thr_ref_delete_unlocked(struct pthread *curthread __unused,
332 	struct pthread *thread)
333 {
334 	if (thread != NULL) {
335 		thread->refcount--;
336 		if ((thread->refcount == 0) && thread->state == PS_DEAD &&
337 		    (thread->tlflags & TLFLAGS_DETACHED) != 0)
338 			THR_GCLIST_ADD(thread);
339 	}
340 }
341 
342 int
343 _thr_find_thread(struct pthread *curthread __unused, struct pthread *thread,
344     int include_dead)
345 {
346 	struct pthread *pthread;
347 
348 	if (thread == NULL)
349 		/* Invalid thread: */
350 		return (EINVAL);
351 
352 	pthread = _thr_hash_find(thread);
353 	if (pthread) {
354 		if (include_dead == 0 && pthread->state == PS_DEAD) {
355 			pthread = NULL;
356 		}
357 	}
358 
359 	/* Return zero if the thread exists: */
360 	return ((pthread != NULL) ? 0 : ESRCH);
361 }
362