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 1.3 2005/03/29 19:26:20 joerg 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 /*
49  * Define a high water mark for the maximum number of threads that
50  * will be cached.  Once this level is reached, any extra threads
51  * will be free()'d.
52  */
53 #define	MAX_CACHED_THREADS	100
54 
55 /*
56  * We've got to keep track of everything that is allocated, not only
57  * to have a speedy free list, but also so they can be deallocated
58  * after a fork().
59  */
60 static TAILQ_HEAD(, pthread)	free_threadq;
61 static umtx_t			free_thread_lock;
62 static umtx_t			tcb_lock;
63 static int			free_thread_count = 0;
64 static int			inited = 0;
65 static u_int64_t		next_uniqueid = 1;
66 
67 LIST_HEAD(thread_hash_head, pthread);
68 #define HASH_QUEUES	128
69 static struct thread_hash_head	thr_hashtable[HASH_QUEUES];
70 #define	THREAD_HASH(thrd)	(((unsigned long)thrd >> 12) % HASH_QUEUES)
71 
72 static void thr_destroy(struct pthread *curthread, struct pthread *thread);
73 
74 void
75 _thr_list_init(void)
76 {
77 	int i;
78 
79 	_gc_count = 0;
80 	_thr_umtx_init(&_thr_list_lock);
81 	TAILQ_INIT(&_thread_list);
82 	TAILQ_INIT(&free_threadq);
83 	_thr_umtx_init(&free_thread_lock);
84 	_thr_umtx_init(&tcb_lock);
85 	if (inited) {
86 		for (i = 0; i < HASH_QUEUES; ++i)
87 			LIST_INIT(&thr_hashtable[i]);
88 	}
89 	inited = 1;
90 }
91 
92 void
93 _thr_gc(struct pthread *curthread)
94 {
95 	struct pthread *td, *td_next;
96 	TAILQ_HEAD(, pthread) worklist;
97 
98 	TAILQ_INIT(&worklist);
99 	THREAD_LIST_LOCK(curthread);
100 
101 	/* Check the threads waiting for GC. */
102 	for (td = TAILQ_FIRST(&_thread_gc_list); td != NULL; td = td_next) {
103 		td_next = TAILQ_NEXT(td, gcle);
104 		if (td->terminated == 0) {
105 			/* make sure we are not still in userland */
106 			continue;
107 		}
108 		_thr_stack_free(&td->attr);
109 		if (((td->tlflags & TLFLAGS_DETACHED) != 0) &&
110 		    (td->refcount == 0)) {
111 			THR_GCLIST_REMOVE(td);
112 			/*
113 			 * The thread has detached and is no longer
114 			 * referenced.  It is safe to remove all
115 			 * remnants of the thread.
116 			 */
117 			THR_LIST_REMOVE(td);
118 			TAILQ_INSERT_HEAD(&worklist, td, gcle);
119 		}
120 	}
121 	THREAD_LIST_UNLOCK(curthread);
122 
123 	while ((td = TAILQ_FIRST(&worklist)) != NULL) {
124 		TAILQ_REMOVE(&worklist, td, gcle);
125 		/*
126 		 * XXX we don't free initial thread, because there might
127 		 * have some code referencing initial thread.
128 		 */
129 		if (td == _thr_initial) {
130 			DBG_MSG("Initial thread won't be freed\n");
131 			continue;
132 		}
133 
134 		DBG_MSG("Freeing thread %p\n", td);
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 tls_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 		thread = malloc(sizeof(struct pthread));
159 		if (thread == NULL)
160 			return (NULL);
161 	}
162 	if (curthread != NULL) {
163 		THR_LOCK_ACQUIRE(curthread, &tcb_lock);
164 		tcb = _tcb_ctor(thread, 0 /* not initial tls */);
165 		THR_LOCK_RELEASE(curthread, &tcb_lock);
166 	} else {
167 		tcb = _tcb_ctor(thread, 1 /* initial tls */);
168 	}
169 	if (tcb != NULL) {
170 		memset(thread, 0, sizeof(*thread));
171 		thread->tcb = tcb;
172 	} else {
173 		thr_destroy(curthread, thread);
174 		thread = NULL;
175 	}
176 	return (thread);
177 }
178 
179 void
180 _thr_free(struct pthread *curthread, struct pthread *thread)
181 {
182 	DBG_MSG("Freeing thread %p\n", thread);
183 	if (thread->name) {
184 		free(thread->name);
185 		thread->name = NULL;
186 	}
187 	/*
188 	 * Always free tcb, as we only know it is part of RTLD TLS
189 	 * block, but don't know its detail and can not assume how
190 	 * it works, so better to avoid caching it here.
191 	 */
192 	if (curthread != NULL) {
193 		THR_LOCK_ACQUIRE(curthread, &tcb_lock);
194 		_tcb_dtor(thread->tcb);
195 		THR_LOCK_RELEASE(curthread, &tcb_lock);
196 	} else {
197 		_tcb_dtor(thread->tcb);
198 	}
199 	thread->tcb = NULL;
200 	if ((curthread == NULL) || (free_thread_count >= MAX_CACHED_THREADS)) {
201 		thr_destroy(curthread, thread);
202 	} else {
203 		/*
204 		 * Add the thread to the free thread list, this also avoids
205 		 * pthread id is reused too quickly, may help some buggy apps.
206 		 */
207 		THR_LOCK_ACQUIRE(curthread, &free_thread_lock);
208 		TAILQ_INSERT_TAIL(&free_threadq, thread, tle);
209 		free_thread_count++;
210 		THR_LOCK_RELEASE(curthread, &free_thread_lock);
211 	}
212 }
213 
214 static void
215 thr_destroy(struct pthread *curthread __unused, struct pthread *thread)
216 {
217 	free(thread);
218 }
219 
220 /*
221  * Add an active thread:
222  *
223  *   o Assign the thread a unique id (which GDB uses to track
224  *     threads.
225  *   o 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 	/*
233 	 * Initialize the unique id (which GDB uses to track
234 	 * threads), add the thread to the list of all threads,
235 	 * and
236 	 */
237 	thread->uniqueid = next_uniqueid++;
238 	THR_LIST_ADD(thread);
239 	if (thread->attr.flags & PTHREAD_DETACHED)
240 		thread->tlflags |= TLFLAGS_DETACHED;
241 	_thread_active_threads++;
242 	THREAD_LIST_UNLOCK(curthread);
243 }
244 
245 /*
246  * Remove an active thread.
247  */
248 void
249 _thr_unlink(struct pthread *curthread, struct pthread *thread)
250 {
251 	THREAD_LIST_LOCK(curthread);
252 	THR_LIST_REMOVE(thread);
253 	_thread_active_threads--;
254 	THREAD_LIST_UNLOCK(curthread);
255 }
256 
257 void
258 _thr_hash_add(struct pthread *thread)
259 {
260 	struct thread_hash_head *head;
261 
262 	head = &thr_hashtable[THREAD_HASH(thread)];
263 	LIST_INSERT_HEAD(head, thread, hle);
264 }
265 
266 void
267 _thr_hash_remove(struct pthread *thread)
268 {
269 	LIST_REMOVE(thread, hle);
270 }
271 
272 struct pthread *
273 _thr_hash_find(struct pthread *thread)
274 {
275 	struct pthread *td;
276 	struct thread_hash_head *head;
277 
278 	head = &thr_hashtable[THREAD_HASH(thread)];
279 	LIST_FOREACH(td, head, hle) {
280 		if (td == thread)
281 			return (thread);
282 	}
283 	return (NULL);
284 }
285 
286 /*
287  * Find a thread in the linked list of active threads and add a reference
288  * to it.  Threads with positive reference counts will not be deallocated
289  * until all references are released.
290  */
291 int
292 _thr_ref_add(struct pthread *curthread, struct pthread *thread,
293     int include_dead)
294 {
295 	int ret;
296 
297 	if (thread == NULL)
298 		/* Invalid thread: */
299 		return (EINVAL);
300 
301 	THREAD_LIST_LOCK(curthread);
302 	if ((ret = _thr_find_thread(curthread, thread, include_dead)) == 0) {
303 		thread->refcount++;
304 	}
305 	THREAD_LIST_UNLOCK(curthread);
306 
307 	/* Return zero if the thread exists: */
308 	return (ret);
309 }
310 
311 void
312 _thr_ref_delete(struct pthread *curthread, struct pthread *thread)
313 {
314 	if (thread != NULL) {
315 		THREAD_LIST_LOCK(curthread);
316 		thread->refcount--;
317 		if ((thread->refcount == 0) &&
318 		    (thread->tlflags & TLFLAGS_GC_SAFE) != 0)
319 			THR_GCLIST_ADD(thread);
320 		THREAD_LIST_UNLOCK(curthread);
321 	}
322 }
323 
324 int
325 _thr_find_thread(struct pthread *curthread, struct pthread *thread,
326     int include_dead)
327 {
328 	struct pthread *pthread;
329 
330 	if (thread == NULL)
331 		/* Invalid thread: */
332 		return (EINVAL);
333 
334 	pthread = _thr_hash_find(thread);
335 	if (pthread) {
336 		if (include_dead == 0 && pthread->state == PS_DEAD) {
337 			pthread = NULL;
338 		}
339 	}
340 
341 	/* Return zero if the thread exists: */
342 	return ((pthread != NULL) ? 0 : ESRCH);
343 }
344