thr_list.c revision 144736 
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: head/lib/libthr/thread/thr_list.c 144736 2005-04-07 06:09:17Z davidxu $
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/*
48 * Define a high water mark for the maximum number of threads that
49 * will be cached.  Once this level is reached, any extra threads
50 * will be free()'d.
51 */
52#define	MAX_CACHED_THREADS	100
53
54/*
55 * We've got to keep track of everything that is allocated, not only
56 * to have a speedy free list, but also so they can be deallocated
57 * after a fork().
58 */
59static TAILQ_HEAD(, pthread)	free_threadq;
60static umtx_t			free_thread_lock;
61static umtx_t			tcb_lock;
62static int			free_thread_count = 0;
63static int			inited = 0;
64
65LIST_HEAD(thread_hash_head, pthread);
66#define HASH_QUEUES	128
67static struct thread_hash_head	thr_hashtable[HASH_QUEUES];
68#define	THREAD_HASH(thrd)	(((unsigned long)thrd >> 8) % HASH_QUEUES)
69
70static void thr_destroy(struct pthread *curthread, struct pthread *thread);
71
72void
73_thr_list_init(void)
74{
75	int i;
76
77	_gc_count = 0;
78	_thr_umtx_init(&_thr_list_lock);
79	TAILQ_INIT(&_thread_list);
80	TAILQ_INIT(&free_threadq);
81	_thr_umtx_init(&free_thread_lock);
82	_thr_umtx_init(&tcb_lock);
83	if (inited) {
84		for (i = 0; i < HASH_QUEUES; ++i)
85			LIST_INIT(&thr_hashtable[i]);
86	}
87	inited = 1;
88}
89
90void
91_thr_gc(struct pthread *curthread)
92{
93	struct pthread *td, *td_next;
94	TAILQ_HEAD(, pthread) worklist;
95
96	TAILQ_INIT(&worklist);
97	THREAD_LIST_LOCK(curthread);
98
99	/* Check the threads waiting for GC. */
100	for (td = TAILQ_FIRST(&_thread_gc_list); td != NULL; td = td_next) {
101		td_next = TAILQ_NEXT(td, gcle);
102		if (td->terminated == 0) {
103			/* make sure we are not still in userland */
104			continue;
105		}
106		_thr_stack_free(&td->attr);
107		if (((td->tlflags & TLFLAGS_DETACHED) != 0) &&
108		    (td->refcount == 0)) {
109			THR_GCLIST_REMOVE(td);
110			/*
111			 * The thread has detached and is no longer
112			 * referenced.  It is safe to remove all
113			 * remnants of the thread.
114			 */
115			THR_LIST_REMOVE(td);
116			TAILQ_INSERT_HEAD(&worklist, td, gcle);
117		}
118	}
119	THREAD_LIST_UNLOCK(curthread);
120
121	while ((td = TAILQ_FIRST(&worklist)) != NULL) {
122		TAILQ_REMOVE(&worklist, td, gcle);
123		/*
124		 * XXX we don't free initial thread, because there might
125		 * have some code referencing initial thread.
126		 */
127		if (td == _thr_initial) {
128			DBG_MSG("Initial thread won't be freed\n");
129			continue;
130		}
131
132		DBG_MSG("Freeing thread %p\n", td);
133		_thr_free(curthread, td);
134	}
135}
136
137struct pthread *
138_thr_alloc(struct pthread *curthread)
139{
140	struct pthread	*thread = NULL;
141	struct tcb	*tcb;
142
143	if (curthread != NULL) {
144		if (GC_NEEDED())
145			_thr_gc(curthread);
146		if (free_thread_count > 0) {
147			THR_LOCK_ACQUIRE(curthread, &free_thread_lock);
148			if ((thread = TAILQ_FIRST(&free_threadq)) != NULL) {
149				TAILQ_REMOVE(&free_threadq, thread, tle);
150				free_thread_count--;
151			}
152			THR_LOCK_RELEASE(curthread, &free_thread_lock);
153		}
154	}
155	if (thread == NULL) {
156		thread = malloc(sizeof(struct pthread));
157		if (thread == NULL)
158			return (NULL);
159	}
160	if (curthread != NULL) {
161		THR_LOCK_ACQUIRE(curthread, &tcb_lock);
162		tcb = _tcb_ctor(thread, 0 /* not initial tls */);
163		THR_LOCK_RELEASE(curthread, &tcb_lock);
164	} else {
165		tcb = _tcb_ctor(thread, 1 /* initial tls */);
166	}
167	if (tcb != NULL) {
168		memset(thread, 0, sizeof(*thread));
169		thread->tcb = tcb;
170	} else {
171		thr_destroy(curthread, thread);
172		thread = NULL;
173	}
174	return (thread);
175}
176
177void
178_thr_free(struct pthread *curthread, struct pthread *thread)
179{
180	DBG_MSG("Freeing thread %p\n", thread);
181	if (thread->name) {
182		free(thread->name);
183		thread->name = NULL;
184	}
185	/*
186	 * Always free tcb, as we only know it is part of RTLD TLS
187	 * block, but don't know its detail and can not assume how
188	 * it works, so better to avoid caching it here.
189	 */
190	if (curthread != NULL) {
191		THR_LOCK_ACQUIRE(curthread, &tcb_lock);
192		_tcb_dtor(thread->tcb);
193		THR_LOCK_RELEASE(curthread, &tcb_lock);
194	} else {
195		_tcb_dtor(thread->tcb);
196	}
197	thread->tcb = NULL;
198	if ((curthread == NULL) || (free_thread_count >= MAX_CACHED_THREADS)) {
199		thr_destroy(curthread, thread);
200	} else {
201		/*
202		 * Add the thread to the free thread list, this also avoids
203		 * pthread id is reused too quickly, may help some buggy apps.
204		 */
205		THR_LOCK_ACQUIRE(curthread, &free_thread_lock);
206		TAILQ_INSERT_TAIL(&free_threadq, thread, tle);
207		free_thread_count++;
208		THR_LOCK_RELEASE(curthread, &free_thread_lock);
209	}
210}
211
212static void
213thr_destroy(struct pthread *curthread __unused, struct pthread *thread)
214{
215	free(thread);
216}
217
218/*
219 * Add the thread to the list of all threads and increment
220 * number of active threads.
221 */
222void
223_thr_link(struct pthread *curthread, struct pthread *thread)
224{
225	THREAD_LIST_LOCK(curthread);
226	THR_LIST_ADD(thread);
227	if (thread->attr.flags & PTHREAD_DETACHED)
228		thread->tlflags |= TLFLAGS_DETACHED;
229	_thread_active_threads++;
230	THREAD_LIST_UNLOCK(curthread);
231}
232
233/*
234 * Remove an active thread.
235 */
236void
237_thr_unlink(struct pthread *curthread, struct pthread *thread)
238{
239	THREAD_LIST_LOCK(curthread);
240	THR_LIST_REMOVE(thread);
241	_thread_active_threads--;
242	THREAD_LIST_UNLOCK(curthread);
243}
244
245void
246_thr_hash_add(struct pthread *thread)
247{
248	struct thread_hash_head *head;
249
250	head = &thr_hashtable[THREAD_HASH(thread)];
251	LIST_INSERT_HEAD(head, thread, hle);
252}
253
254void
255_thr_hash_remove(struct pthread *thread)
256{
257	LIST_REMOVE(thread, hle);
258}
259
260struct pthread *
261_thr_hash_find(struct pthread *thread)
262{
263	struct pthread *td;
264	struct thread_hash_head *head;
265
266	head = &thr_hashtable[THREAD_HASH(thread)];
267	LIST_FOREACH(td, head, hle) {
268		if (td == thread)
269			return (thread);
270	}
271	return (NULL);
272}
273
274/*
275 * Find a thread in the linked list of active threads and add a reference
276 * to it.  Threads with positive reference counts will not be deallocated
277 * until all references are released.
278 */
279int
280_thr_ref_add(struct pthread *curthread, struct pthread *thread,
281    int include_dead)
282{
283	int ret;
284
285	if (thread == NULL)
286		/* Invalid thread: */
287		return (EINVAL);
288
289	THREAD_LIST_LOCK(curthread);
290	if ((ret = _thr_find_thread(curthread, thread, include_dead)) == 0) {
291		thread->refcount++;
292	}
293	THREAD_LIST_UNLOCK(curthread);
294
295	/* Return zero if the thread exists: */
296	return (ret);
297}
298
299void
300_thr_ref_delete(struct pthread *curthread, struct pthread *thread)
301{
302	if (thread != NULL) {
303		THREAD_LIST_LOCK(curthread);
304		thread->refcount--;
305		if ((thread->refcount == 0) &&
306		    (thread->tlflags & TLFLAGS_GC_SAFE) != 0)
307			THR_GCLIST_ADD(thread);
308		THREAD_LIST_UNLOCK(curthread);
309	}
310}
311
312int
313_thr_find_thread(struct pthread *curthread, struct pthread *thread,
314    int include_dead)
315{
316	struct pthread *pthread;
317
318	if (thread == NULL)
319		/* Invalid thread: */
320		return (EINVAL);
321
322	pthread = _thr_hash_find(thread);
323	if (pthread) {
324		if (include_dead == 0 && pthread->state == PS_DEAD) {
325			pthread = NULL;
326		}
327	}
328
329	/* Return zero if the thread exists: */
330	return ((pthread != NULL) ? 0 : ESRCH);
331}
332