6/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 /*
  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  */
  59 static TAILQ_HEAD(, pthread)    free_threadq;
  60 static umtx_t                   free_thread_lock;
  61 static umtx_t                   tcb_lock;
  62 static int                      free_thread_count = 0;
  63 static int                      inited = 0;
  64
  65 LIST_HEAD(thread_hash_head, pthread);
  66 #define HASH_QUEUES     128
  67 static struct thread_hash_head  thr_hashtable[HASH_QUEUES];
  68 #define THREAD_HASH(thrd)       (((unsigned long)thrd >> 8) % HASH_QUEUES)
  69
  70 static void thr_destroy(struct pthread *curthread, struct pthread *thread);
  71
  72 void
  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
  90 void
  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->tid != TID_TERMINATED) {
 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                 _thr_free(curthread, td);
 133         }
 134 }
 135
 136 struct pthread *
 137 _thr_alloc(struct pthread *curthread)
 138 {
 139         struct pthread  *thread = NULL;
 140         struct tcb      *tcb;
 141
 142         if (curthread != NULL) {
 143                 if (GC_NEEDED())
 144                         _thr_gc(curthread);
 145                 if (free_thread_count > 0) {
 146                         THR_LOCK_ACQUIRE(curthread, &free_thread_lock);
 147                         if ((thread = TAILQ_FIRST(&free_threadq)) != NULL) {
 148                                 TAILQ_REMOVE(&free_threadq, thread, tle);
 149                                 free_thread_count--;
 150                         }
 151                         THR_LOCK_RELEASE(curthread, &free_thread_lock);
 152                 }
 153         }
 154         if (thread == NULL) {
 155                 thread = malloc(sizeof(struct pthread));
 156                 if (thread == NULL)
 157                         return (NULL);
 158         }
 159         if (curthread != NULL) {
 160                 THR_LOCK_ACQUIRE(curthread, &tcb_lock);
 161                 tcb = _tcb_ctor(thread, 0 /* not initial tls */);
 162                 THR_LOCK_RELEASE(curthread, &tcb_lock);
 163         } else {
 164                 tcb = _tcb_ctor(thread, 1 /* initial tls */);
 165         }
 166         if (tcb != NULL) {
 167                 memset(thread, 0, sizeof(*thread));
 168                 thread->tcb = tcb;
 169         } else {
 170                 thr_destroy(curthread, thread);
 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         if (thread->name) {
 181                 free(thread->name);
 182                 thread->name = NULL;
 183         }
 184         /*
 185          * Always free tcb, as we only know it is part of RTLD TLS
 186          * block, but don't know its detail and can not assume how
 187          * it works, so better to avoid caching it here.
 188          */
 189         if (curthread != NULL) {
 190                 THR_LOCK_ACQUIRE(curthread, &tcb_lock);
 191                 _tcb_dtor(thread->tcb);
 192                 THR_LOCK_RELEASE(curthread, &tcb_lock);
 193         } else {
 194                 _tcb_dtor(thread->tcb);
 195         }
 196         thread->tcb = NULL;
 197         if ((curthread == NULL) || (free_thread_count >= MAX_CACHED_THREADS)) {
 198                 thr_destroy(curthread, thread);
 199         } else {
 200                 /*
 201                  * Add the thread to the free thread list, this also avoids
 202                  * pthread id is reused too quickly, may help some buggy apps.
 203                  */
 204                 THR_LOCK_ACQUIRE(curthread, &free_thread_lock);
 205                 TAILQ_INSERT_TAIL(&free_threadq, thread, tle);
 206                 free_thread_count++;
 207                 THR_LOCK_RELEASE(curthread, &free_thread_lock);
 208         }
 209 }
 210
 211 static void
 212 thr_destroy(struct pthread *curthread __unused, struct pthread *thread)
 213 {
 214         free(thread);
 215 }
 216
 217 /*
 218  * Add the thread to the list of all threads and increment
 219  * number of active threads.
 220  */
 221 void
 222 _thr_link(struct pthread *curthread, struct pthread *thread)
 223 {
 224         THREAD_LIST_LOCK(curthread);
 225         THR_LIST_ADD(thread);
 226         _thread_active_threads++;
 227         THREAD_LIST_UNLOCK(curthread);
 228 }
 229
 230 /*
 231  * Remove an active thread.
 232  */
 233 void
 234 _thr_unlink(struct pthread *curthread, struct pthread *thread)
 235 {
 236         THREAD_LIST_LOCK(curthread);
 237         THR_LIST_REMOVE(thread);
 238         _thread_active_threads--;
 239         THREAD_LIST_UNLOCK(curthread);
 240 }
 241
 242 void
 243 _thr_hash_add(struct pthread *thread)
 244 {
 245         struct thread_hash_head *head;
 246
 247         head = &thr_hashtable[THREAD_HASH(thread)];
 248         LIST_INSERT_HEAD(head, thread, hle);
 249 }
 250
 251 void
 252 _thr_hash_remove(struct pthread *thread)
 253 {
 254         LIST_REMOVE(thread, hle);
 255 }
 256
 257 struct pthread *
 258 _thr_hash_find(struct pthread *thread)
 259 {
 260         struct pthread *td;
 261         struct thread_hash_head *head;
 262
 263         head = &thr_hashtable[THREAD_HASH(thread)];
 264         LIST_FOREACH(td, head, hle) {
 265                 if (td == thread)
 266                         return (thread);
 267         }
 268         return (NULL);
 269 }
 270
 271 /*
 272  * Find a thread in the linked list of active threads and add a reference
 273  * to it.  Threads with positive reference counts will not be deallocated
 274  * until all references are released.
 275  */
 276 int
 277 _thr_ref_add(struct pthread *curthread, struct pthread *thread,
 278     int include_dead)
 279 {
 280         int ret;
 281
 282         if (thread == NULL)
 283                 /* Invalid thread: */
 284                 return (EINVAL);
 285
 286         THREAD_LIST_LOCK(curthread);
 287         if ((ret = _thr_find_thread(curthread, thread, include_dead)) == 0) {
 288                 thread->refcount++;
 289         }
 290         THREAD_LIST_UNLOCK(curthread);
 291
 292         /* Return zero if the thread exists: */
 293         return (ret);
 294 }
 295
 296 void
 297 _thr_ref_delete(struct pthread *curthread, struct pthread *thread)
 298 {
 299         THREAD_LIST_LOCK(curthread);
 300         _thr_ref_delete_unlocked(curthread, thread);
 301         THREAD_LIST_UNLOCK(curthread);
 302 }
 303
 304 void
 305 _thr_ref_delete_unlocked(struct pthread *curthread, struct pthread *thread)
 306 {
 307         if (thread != NULL) {
 308                 thread->refcount--;
 309                 if ((thread->refcount == 0) && thread->state == PS_DEAD &&
 310                     (thread->tlflags & TLFLAGS_DETACHED) != 0)
 311                         THR_GCLIST_ADD(thread);
 312         }
 313 }
 314
 315 int
 316 _thr_find_thread(struct pthread *curthread, struct pthread *thread,
 317     int include_dead)
 318 {
 319         struct pthread *pthread;
 320
 321         if (thread == NULL)
 322                 /* Invalid thread: */
 323                 return (EINVAL);
 324
 325         pthread = _thr_hash_find(thread);
 326         if (pthread) {
 327                 if (include_dead == 0 && pthread->state == PS_DEAD) {
 328                         pthread = NULL;
 329                 }
 330         }
 331
 332         /* Return zero if the thread exists: */
 333         return ((pthread != NULL) ? 0 : ESRCH);
 334 }