lib/libthr/thread/thr_list.c

   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  */
  61 static TAILQ_HEAD(, pthread)    free_threadq;
  62 static struct umutex            free_thread_lock = DEFAULT_UMUTEX;
  63 static struct umutex            tcb_lock = DEFAULT_UMUTEX;
  64 static int                      free_thread_count = 0;
  65 static int                      inited = 0;
  66 static int                      total_threads;
  67
  68 LIST_HEAD(thread_hash_head, pthread);
  69 #define HASH_QUEUES     128
  70 static struct thread_hash_head  thr_hashtable[HASH_QUEUES];
  71 #define THREAD_HASH(thrd)       (((unsigned long)thrd >> 8) % HASH_QUEUES)
  72
  73 static void thr_destroy(struct pthread *curthread, struct pthread *thread);
  74
  75 void
  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
  94 void
  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
 130 struct 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 = malloc(sizeof(struct pthread));
 153                 if (thread == NULL) {
 154                         atomic_fetchadd_int(&total_threads, -1);
 155                         return (NULL);
 156                 }
 157         }
 158         if (curthread != NULL) {
 159                 THR_LOCK_ACQUIRE(curthread, &tcb_lock);
 160                 tcb = _tcb_ctor(thread, 0 /* not initial tls */);
 161                 THR_LOCK_RELEASE(curthread, &tcb_lock);
 162         } else {
 163                 tcb = _tcb_ctor(thread, 1 /* initial tls */);
 164         }
 165         if (tcb != NULL) {
 166                 memset(thread, 0, sizeof(*thread));
 167                 thread->tcb = tcb;
 168         } else {
 169                 thr_destroy(curthread, thread);
 170                 atomic_fetchadd_int(&total_threads, -1);
 171                 thread = NULL;
 172         }
 173         return (thread);
 174 }
 175
 176 void
 177 _thr_free(struct pthread *curthread, struct pthread *thread)
 178 {
 179         DBG_MSG("Freeing thread %p\n", thread);
 180
 181         /*
 182          * Always free tcb, as we only know it is part of RTLD TLS
 183          * block, but don't know its detail and can not assume how
 184          * it works, so better to avoid caching it here.
 185          */
 186         if (curthread != NULL) {
 187                 THR_LOCK_ACQUIRE(curthread, &tcb_lock);
 188                 _tcb_dtor(thread->tcb);
 189                 THR_LOCK_RELEASE(curthread, &tcb_lock);
 190         } else {
 191                 _tcb_dtor(thread->tcb);
 192         }
 193         thread->tcb = NULL;
 194         if ((curthread == NULL) || (free_thread_count >= MAX_CACHED_THREADS)) {
 195                 thr_destroy(curthread, thread);
 196                 atomic_fetchadd_int(&total_threads, -1);
 197         } else {
 198                 /*
 199                  * Add the thread to the free thread list, this also avoids
 200                  * pthread id is reused too quickly, may help some buggy apps.
 201                  */
 202                 THR_LOCK_ACQUIRE(curthread, &free_thread_lock);
 203                 TAILQ_INSERT_TAIL(&free_threadq, thread, tle);
 204                 free_thread_count++;
 205                 THR_LOCK_RELEASE(curthread, &free_thread_lock);
 206         }
 207 }
 208
 209 static void
 210 thr_destroy(struct pthread *curthread __unused, struct pthread *thread)
 211 {
 212         free(thread);
 213 }
 214
 215 /*
 216  * Add the thread to the list of all threads and increment
 217  * number of active threads.
 218  */
 219 void
 220 _thr_link(struct pthread *curthread, struct pthread *thread)
 221 {
 222         THREAD_LIST_WRLOCK(curthread);
 223         THR_LIST_ADD(thread);
 224         THREAD_LIST_UNLOCK(curthread);
 225         atomic_add_int(&_thread_active_threads, 1);
 226 }
 227
 228 /*
 229  * Remove an active thread.
 230  */
 231 void
 232 _thr_unlink(struct pthread *curthread, struct pthread *thread)
 233 {
 234         THREAD_LIST_WRLOCK(curthread);
 235         THR_LIST_REMOVE(thread);
 236         THREAD_LIST_UNLOCK(curthread);
 237         atomic_add_int(&_thread_active_threads, -1);
 238 }
 239
 240 void
 241 _thr_hash_add(struct pthread *thread)
 242 {
 243         struct thread_hash_head *head;
 244
 245         head = &thr_hashtable[THREAD_HASH(thread)];
 246         LIST_INSERT_HEAD(head, thread, hle);
 247 }
 248
 249 void
 250 _thr_hash_remove(struct pthread *thread)
 251 {
 252         LIST_REMOVE(thread, hle);
 253 }
 254
 255 struct pthread *
 256 _thr_hash_find(struct pthread *thread)
 257 {
 258         struct pthread *td;
 259         struct thread_hash_head *head;
 260
 261         head = &thr_hashtable[THREAD_HASH(thread)];
 262         LIST_FOREACH(td, head, hle) {
 263                 if (td == thread)
 264                         return (thread);
 265         }
 266         return (NULL);
 267 }
 268
 269 /*
 270  * Find a thread in the linked list of active threads and add a reference
 271  * to it.  Threads with positive reference counts will not be deallocated
 272  * until all references are released.
 273  */
 274 int
 275 _thr_ref_add(struct pthread *curthread, struct pthread *thread,
 276     int include_dead)
 277 {
 278         int ret;
 279
 280         if (thread == NULL)
 281                 /* Invalid thread: */
 282                 return (EINVAL);
 283
 284         if ((ret = _thr_find_thread(curthread, thread, include_dead)) == 0) {
 285                 thread->refcount++;
 286                 THR_CRITICAL_ENTER(curthread);
 287                 THR_THREAD_UNLOCK(curthread, thread);
 288         }
 289
 290         /* Return zero if the thread exists: */
 291         return (ret);
 292 }
 293
 294 void
 295 _thr_ref_delete(struct pthread *curthread, struct pthread *thread)
 296 {
 297         THR_THREAD_LOCK(curthread, thread);
 298         thread->refcount--;
 299         _thr_try_gc(curthread, thread);
 300         THR_CRITICAL_LEAVE(curthread);
 301 }
 302
 303 /* entered with thread lock held, exit with thread lock released */
 304 void
 305 _thr_try_gc(struct pthread *curthread, struct pthread *thread)
 306 {
 307         if (THR_SHOULD_GC(thread)) {
 308                 THR_REF_ADD(curthread, thread);
 309                 THR_THREAD_UNLOCK(curthread, thread);
 310                 THREAD_LIST_WRLOCK(curthread);
 311                 THR_THREAD_LOCK(curthread, thread);
 312                 THR_REF_DEL(curthread, thread);
 313                 if (THR_SHOULD_GC(thread)) {
 314                         THR_LIST_REMOVE(thread);
 315                         THR_GCLIST_ADD(thread);
 316                 }
 317                 THR_THREAD_UNLOCK(curthread, thread);
 318                 THREAD_LIST_UNLOCK(curthread);
 319         } else {
 320                 THR_THREAD_UNLOCK(curthread, thread);
 321         }
 322 }
 323
 324 /* return with thread lock held if thread is found */
 325 int
 326 _thr_find_thread(struct pthread *curthread, struct pthread *thread,
 327     int include_dead)
 328 {
 329         struct pthread *pthread;
 330         int ret;
 331
 332         if (thread == NULL)
 333                 return (EINVAL);
 334
 335         ret = 0;
 336         THREAD_LIST_RDLOCK(curthread);
 337         pthread = _thr_hash_find(thread);
 338         if (pthread) {
 339                 THR_THREAD_LOCK(curthread, pthread);
 340                 if (include_dead == 0 && pthread->state == PS_DEAD) {
 341                         THR_THREAD_UNLOCK(curthread, pthread);
 342                         ret = ESRCH;
 343                 }
 344         } else {
 345                 ret = ESRCH;
 346         }
 347         THREAD_LIST_UNLOCK(curthread);
 348         return (ret);
 349 }