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 */
61static TAILQ_HEAD(, pthread)	free_threadq;
62static struct umutex		free_thread_lock = DEFAULT_UMUTEX;
63static struct umutex		tcb_lock = DEFAULT_UMUTEX;
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_urwlock_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
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_WRLOCK(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		THR_GCLIST_REMOVE(td);
111		TAILQ_INSERT_HEAD(&worklist, td, gcle);
112	}
113	THREAD_LIST_UNLOCK(curthread);
114
115	while ((td = TAILQ_FIRST(&worklist)) != NULL) {
116		TAILQ_REMOVE(&worklist, td, gcle);
117		/*
118		 * XXX we don't free initial thread, because there might
119		 * have some code referencing initial thread.
120		 */
121		if (td == _thr_initial) {
122			DBG_MSG("Initial thread won't be freed\n");
123			continue;
124		}
125
126		_thr_free(curthread, td);
127	}
128}
129
130struct pthread *
131_thr_alloc(struct pthread *curthread)
132{
133	struct pthread	*thread = NULL;
134	struct tcb	*tcb;
135
136	if (curthread != NULL) {
137		if (GC_NEEDED())
138			_thr_gc(curthread);
139		if (free_thread_count > 0) {
140			THR_LOCK_ACQUIRE(curthread, &free_thread_lock);
141			if ((thread = TAILQ_FIRST(&free_threadq)) != NULL) {
142				TAILQ_REMOVE(&free_threadq, thread, tle);
143				free_thread_count--;
144			}
145			THR_LOCK_RELEASE(curthread, &free_thread_lock);
146		}
147	}
148	if (thread == NULL) {
149		if (total_threads > MAX_THREADS)
150			return (NULL);
151		atomic_fetchadd_int(&total_threads, 1);
152		thread = calloc(1, sizeof(struct pthread));
153		if (thread == NULL) {
154			atomic_fetchadd_int(&total_threads, -1);
155			return (NULL);
156		}
157		if ((thread->sleepqueue = _sleepq_alloc()) == NULL ||
158		    (thread->wake_addr = _thr_alloc_wake_addr()) == NULL) {
159			thr_destroy(curthread, thread);
160			atomic_fetchadd_int(&total_threads, -1);
161			return (NULL);
162		}
163	} else {
164		bzero(&thread->_pthread_startzero,
165			__rangeof(struct pthread, _pthread_startzero, _pthread_endzero));
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		thread->tcb = tcb;
176	} else {
177		thr_destroy(curthread, thread);
178		atomic_fetchadd_int(&total_threads, -1);
179		thread = NULL;
180	}
181	return (thread);
182}
183
184void
185_thr_free(struct pthread *curthread, struct pthread *thread)
186{
187	DBG_MSG("Freeing thread %p\n", thread);
188
189	/*
190	 * Always free tcb, as we only know it is part of RTLD TLS
191	 * block, but don't know its detail and can not assume how
192	 * it works, so better to avoid caching it here.
193	 */
194	if (curthread != NULL) {
195		THR_LOCK_ACQUIRE(curthread, &tcb_lock);
196		_tcb_dtor(thread->tcb);
197		THR_LOCK_RELEASE(curthread, &tcb_lock);
198	} else {
199		_tcb_dtor(thread->tcb);
200	}
201	thread->tcb = NULL;
202	if ((curthread == NULL) || (free_thread_count >= MAX_CACHED_THREADS)) {
203		thr_destroy(curthread, thread);
204		atomic_fetchadd_int(&total_threads, -1);
205	} else {
206		/*
207		 * Add the thread to the free thread list, this also avoids
208		 * pthread id is reused too quickly, may help some buggy apps.
209		 */
210		THR_LOCK_ACQUIRE(curthread, &free_thread_lock);
211		TAILQ_INSERT_TAIL(&free_threadq, thread, tle);
212		free_thread_count++;
213		THR_LOCK_RELEASE(curthread, &free_thread_lock);
214	}
215}
216
217static void
218thr_destroy(struct pthread *curthread __unused, struct pthread *thread)
219{
220	if (thread->sleepqueue != NULL)
221		_sleepq_free(thread->sleepqueue);
222	if (thread->wake_addr != NULL)
223		_thr_release_wake_addr(thread->wake_addr);
224	free(thread);
225}
226
227/*
228 * Add the thread to the list of all threads and increment
229 * number of active threads.
230 */
231void
232_thr_link(struct pthread *curthread, struct pthread *thread)
233{
234	THREAD_LIST_WRLOCK(curthread);
235	THR_LIST_ADD(thread);
236	THREAD_LIST_UNLOCK(curthread);
237	atomic_add_int(&_thread_active_threads, 1);
238}
239
240/*
241 * Remove an active thread.
242 */
243void
244_thr_unlink(struct pthread *curthread, struct pthread *thread)
245{
246	THREAD_LIST_WRLOCK(curthread);
247	THR_LIST_REMOVE(thread);
248	THREAD_LIST_UNLOCK(curthread);
249	atomic_add_int(&_thread_active_threads, -1);
250}
251
252void
253_thr_hash_add(struct pthread *thread)
254{
255	struct thread_hash_head *head;
256
257	head = &thr_hashtable[THREAD_HASH(thread)];
258	LIST_INSERT_HEAD(head, thread, hle);
259}
260
261void
262_thr_hash_remove(struct pthread *thread)
263{
264	LIST_REMOVE(thread, hle);
265}
266
267struct pthread *
268_thr_hash_find(struct pthread *thread)
269{
270	struct pthread *td;
271	struct thread_hash_head *head;
272
273	head = &thr_hashtable[THREAD_HASH(thread)];
274	LIST_FOREACH(td, head, hle) {
275		if (td == thread)
276			return (thread);
277	}
278	return (NULL);
279}
280
281/*
282 * Find a thread in the linked list of active threads and add a reference
283 * to it.  Threads with positive reference counts will not be deallocated
284 * until all references are released.
285 */
286int
287_thr_ref_add(struct pthread *curthread, struct pthread *thread,
288    int include_dead)
289{
290	int ret;
291
292	if (thread == NULL)
293		/* Invalid thread: */
294		return (EINVAL);
295
296	if ((ret = _thr_find_thread(curthread, thread, include_dead)) == 0) {
297		thread->refcount++;
298		THR_CRITICAL_ENTER(curthread);
299		THR_THREAD_UNLOCK(curthread, thread);
300	}
301
302	/* Return zero if the thread exists: */
303	return (ret);
304}
305
306void
307_thr_ref_delete(struct pthread *curthread, struct pthread *thread)
308{
309	THR_THREAD_LOCK(curthread, thread);
310	thread->refcount--;
311	_thr_try_gc(curthread, thread);
312	THR_CRITICAL_LEAVE(curthread);
313}
314
315/* entered with thread lock held, exit with thread lock released */
316void
317_thr_try_gc(struct pthread *curthread, struct pthread *thread)
318{
319	if (THR_SHOULD_GC(thread)) {
320		THR_REF_ADD(curthread, thread);
321		THR_THREAD_UNLOCK(curthread, thread);
322		THREAD_LIST_WRLOCK(curthread);
323		THR_THREAD_LOCK(curthread, thread);
324		THR_REF_DEL(curthread, thread);
325		if (THR_SHOULD_GC(thread)) {
326			THR_LIST_REMOVE(thread);
327			THR_GCLIST_ADD(thread);
328		}
329		THR_THREAD_UNLOCK(curthread, thread);
330		THREAD_LIST_UNLOCK(curthread);
331	} else {
332		THR_THREAD_UNLOCK(curthread, thread);
333	}
334}
335
336/* return with thread lock held if thread is found */
337int
338_thr_find_thread(struct pthread *curthread, struct pthread *thread,
339    int include_dead)
340{
341	struct pthread *pthread;
342	int ret;
343
344	if (thread == NULL)
345		return (EINVAL);
346
347	ret = 0;
348	THREAD_LIST_RDLOCK(curthread);
349	pthread = _thr_hash_find(thread);
350	if (pthread) {
351		THR_THREAD_LOCK(curthread, pthread);
352		if (include_dead == 0 && pthread->state == PS_DEAD) {
353			THR_THREAD_UNLOCK(curthread, pthread);
354			ret = ESRCH;
355		}
356	} else {
357		ret = ESRCH;
358	}
359	THREAD_LIST_UNLOCK(curthread);
360	return (ret);
361}
362