thr_list.c revision 160426 
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 160426 2006-07-17 09:23:44Z delphij $
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 */
61static TAILQ_HEAD(, pthread)	free_threadq;
62static umtx_t			free_thread_lock;
63static umtx_t			tcb_lock;
64static int			free_thread_count = 0;
65static int			inited = 0;
66static int			total_threads;
67
68LIST_HEAD(thread_hash_head, pthread);
69#define HASH_QUEUES	128
70static struct thread_hash_head	thr_hashtable[HASH_QUEUES];
71#define	THREAD_HASH(thrd)	(((unsigned long)thrd >> 8) % HASH_QUEUES)
72
73static void thr_destroy(struct pthread *curthread, struct pthread *thread);
74
75void
76_thr_list_init(void)
77{
78	int i;
79
80	_gc_count = 0;
81	total_threads = 1;
82	_thr_umtx_init(&_thr_list_lock);
83	TAILQ_INIT(&_thread_list);
84	TAILQ_INIT(&free_threadq);
85	_thr_umtx_init(&free_thread_lock);
86	_thr_umtx_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
94void
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
139struct 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
185void
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
218static void
219thr_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 */
228void
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 */
240void
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
249void
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
258void
259_thr_hash_remove(struct pthread *thread)
260{
261	LIST_REMOVE(thread, hle);
262}
263
264struct 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 */
283int
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	}
297	THREAD_LIST_UNLOCK(curthread);
298
299	/* Return zero if the thread exists: */
300	return (ret);
301}
302
303void
304_thr_ref_delete(struct pthread *curthread, struct pthread *thread)
305{
306	THREAD_LIST_LOCK(curthread);
307	_thr_ref_delete_unlocked(curthread, thread);
308	THREAD_LIST_UNLOCK(curthread);
309}
310
311void
312_thr_ref_delete_unlocked(struct pthread *curthread __unused,
313	struct pthread *thread)
314{
315	if (thread != NULL) {
316		thread->refcount--;
317		if ((thread->refcount == 0) && thread->state == PS_DEAD &&
318		    (thread->tlflags & TLFLAGS_DETACHED) != 0)
319			THR_GCLIST_ADD(thread);
320	}
321}
322
323int
324_thr_find_thread(struct pthread *curthread __unused, struct pthread *thread,
325    int include_dead)
326{
327	struct pthread *pthread;
328
329	if (thread == NULL)
330		/* Invalid thread: */
331		return (EINVAL);
332
333	pthread = _thr_hash_find(thread);
334	if (pthread) {
335		if (include_dead == 0 && pthread->state == PS_DEAD) {
336			pthread = NULL;
337		}
338	}
339
340	/* Return zero if the thread exists: */
341	return ((pthread != NULL) ? 0 : ESRCH);
342}
343