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_umutex_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_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
 139 struct 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
 185 void
 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
 218 static void
 219 thr_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  */
 228 void
 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  */
 240 void
 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
 249 void
 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
 258 void
 259 _thr_hash_remove(struct pthread *thread)
 260 {
 261         LIST_REMOVE(thread, hle);
 262 }
 263
 264 struct 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  */
 283 int
 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                 THR_CRITICAL_ENTER(curthread);
 297         }
 298         THREAD_LIST_UNLOCK(curthread);
 299
 300         /* Return zero if the thread exists: */
 301         return (ret);
 302 }
 303
 304 void
 305 _thr_ref_delete(struct pthread *curthread, struct pthread *thread)
 306 {
 307         THREAD_LIST_LOCK(curthread);
 308         _thr_ref_delete_unlocked(curthread, thread);
 309         THREAD_LIST_UNLOCK(curthread);
 310 }
 311
 312 void
 313 _thr_ref_delete_unlocked(struct pthread *curthread,
 314         struct pthread *thread)
 315 {
 316         if (thread != NULL) {
 317                 thread->refcount--;
 318                 if ((thread->refcount == 0) && thread->state == PS_DEAD &&
 319                     (thread->tlflags & TLFLAGS_DETACHED) != 0)
 320                         THR_GCLIST_ADD(thread);
 321                 THR_CRITICAL_LEAVE(curthread);
 322         }
 323 }
 324
 325 int
 326 _thr_find_thread(struct pthread *curthread __unused, struct pthread *thread,
 327     int include_dead)
 328 {
 329         struct pthread *pthread;
 330
 331         if (thread == NULL)
 332                 /* Invalid thread: */
 333                 return (EINVAL);
 334
 335         pthread = _thr_hash_find(thread);
 336         if (pthread) {
 337                 if (include_dead == 0 && pthread->state == PS_DEAD) {
 338                         pthread = NULL;
 339                 }
 340         }
 341
 342         /* Return zero if the thread exists: */
 343         return ((pthread != NULL) ? 0 : ESRCH);
 344 }