lib/libc_r/uthread/uthread_gc.c

   1 /*
   2  * Copyright (c) 1998 John Birrell <jb@cimlogic.com.au>
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by John Birrell.
  16  * 4. Neither the name of the author nor the names of any co-contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * $FreeBSD: src/lib/libc_r/uthread/uthread_gc.c,v 1.11.2.5 2002/10/22 14:44:03 fjoe Exp $
  33  *
  34  * Garbage collector thread. Frees memory allocated for dead threads.
  35  *
  36  */
  37 #include <errno.h>
  38 #include <time.h>
  39 #include <stdlib.h>
  40 #include <unistd.h>
  41 #include <sys/types.h>
  42 #include <sys/mman.h>
  43 #include <pthread.h>
  44 #include "pthread_private.h"
  45
  46 pthread_addr_t
  47 _thread_gc(pthread_addr_t arg)
  48 {
  49         struct pthread  *curthread = _get_curthread();
  50         int             f_debug;
  51         int             f_done = 0;
  52         int             ret;
  53         sigset_t        mask;
  54         pthread_t       pthread;
  55         pthread_t       pthread_cln;
  56         struct timespec abstime;
  57         void            *p_stack;
  58
  59         /* Block all signals */
  60         sigfillset(&mask);
  61         pthread_sigmask(SIG_BLOCK, &mask, NULL);
  62
  63         /* Mark this thread as a library thread (not a user thread). */
  64         curthread->flags |= PTHREAD_FLAGS_PRIVATE;
  65
  66         /* Set a debug flag based on an environment variable. */
  67         f_debug = (getenv("LIBC_R_DEBUG") != NULL);
  68
  69         /* Set the name of this thread. */
  70         pthread_set_name_np(curthread,"GC");
  71
  72         while (!f_done) {
  73                 /* Check if debugging this application. */
  74                 if (f_debug)
  75                         /* Dump thread info to file. */
  76                         _thread_dump_info();
  77
  78                 /*
  79                  * Defer signals to protect the scheduling queues from
  80                  * access by the signal handler:
  81                  */
  82                 _thread_kern_sig_defer();
  83
  84                 /* Check if this is the last running thread: */
  85                 if (TAILQ_FIRST(&_thread_list) == curthread &&
  86                     TAILQ_NEXT(curthread, tle) == NULL)
  87                         /*
  88                          * This is the last thread, so it can exit
  89                          * now.
  90                          */
  91                         f_done = 1;
  92
  93                 /*
  94                  * Undefer and handle pending signals, yielding if
  95                  * necessary:
  96                  */
  97                 _thread_kern_sig_undefer();
  98
  99                 /*
 100                  * Lock the garbage collector mutex which ensures that
 101                  * this thread sees another thread exit:
 102                  */
 103                 if (pthread_mutex_lock(&_gc_mutex) != 0)
 104                         PANIC("Cannot lock gc mutex");
 105
 106                 /* No stack of thread structure to free yet: */
 107                 p_stack = NULL;
 108                 pthread_cln = NULL;
 109
 110                 /*
 111                  * Enter a loop to search for the first dead thread that
 112                  * has memory to free.
 113                  */
 114                 for (pthread = TAILQ_FIRST(&_dead_list);
 115                      p_stack == NULL && pthread_cln == NULL && pthread != NULL;
 116                      pthread = TAILQ_NEXT(pthread, dle)) {
 117                         /* Check if the initial thread: */
 118                         if (pthread == _thread_initial) {
 119                                 /* Don't destroy the initial thread. */
 120                         }
 121                         /*
 122                          * Check if this thread has detached:
 123                          */
 124                         else if ((pthread->attr.flags &
 125                             PTHREAD_DETACHED) != 0) {
 126                                 /* Remove this thread from the dead list: */
 127                                 TAILQ_REMOVE(&_dead_list, pthread, dle);
 128
 129                                 /*
 130                                  * Check if the stack was not specified by
 131                                  * the caller to pthread_create() and has not
 132                                  * been destroyed yet:
 133                                  */
 134                                 if (pthread->attr.stackaddr_attr == NULL &&
 135                                     pthread->stack != NULL) {
 136                                         if (pthread->attr.stacksize_attr
 137                                             == PTHREAD_STACK_DEFAULT) {
 138                                                 /*
 139                                                  * Default-size stack.  Cache
 140                                                  * it:
 141                                                  */
 142                                                 struct stack    *spare_stack;
 143
 144                                                 spare_stack
 145                                                     = (pthread->stack
 146                                                        + PTHREAD_STACK_DEFAULT
 147                                                        - sizeof(struct stack));
 148                                                 SLIST_INSERT_HEAD(&_stackq,
 149                                                                   spare_stack,
 150                                                                   qe);
 151                                         } else {
 152                                                 /*
 153                                                  * Non-standard stack size.
 154                                                  * free() it outside the locks.
 155                                                  */
 156                                                 p_stack = pthread->stack;
 157                                         }
 158                                 }
 159
 160                                 /*
 161                                  * Point to the thread structure that must
 162                                  * be freed outside the locks:
 163                                  */
 164                                 pthread_cln = pthread;
 165
 166                         } else {
 167                                 /*
 168                                  * This thread has not detached, so do
 169                                  * not destroy it.
 170                                  *
 171                                  * Check if the stack was not specified by
 172                                  * the caller to pthread_create() and has not
 173                                  * been destroyed yet:
 174                                  */
 175                                 if (pthread->attr.stackaddr_attr == NULL &&
 176                                     pthread->stack != NULL) {
 177                                         if (pthread->attr.stacksize_attr
 178                                             == PTHREAD_STACK_DEFAULT) {
 179                                                 /*
 180                                                  * Default-size stack.  Cache
 181                                                  * it:
 182                                                  */
 183                                                 struct stack    *spare_stack;
 184
 185                                                 spare_stack
 186                                                     = (pthread->stack
 187                                                        + PTHREAD_STACK_DEFAULT
 188                                                        - sizeof(struct stack));
 189                                                 SLIST_INSERT_HEAD(&_stackq,
 190                                                                   spare_stack,
 191                                                                   qe);
 192                                         } else {
 193                                                 /*
 194                                                  * Non-standard stack size.
 195                                                  * free() it outside the locks:
 196                                                  */
 197                                                 p_stack = pthread->stack;
 198                                         }
 199
 200                                         /*
 201                                          * NULL the stack pointer now
 202                                          * that the memory has been freed:
 203                                          */
 204                                         pthread->stack = NULL;
 205                                 }
 206                         }
 207                 }
 208
 209                 /*
 210                  * Check if this is not the last thread and there is no
 211                  * memory to free this time around.
 212                  */
 213                 if (!f_done && p_stack == NULL && pthread_cln == NULL) {
 214                         /* Get the current time. */
 215                         if (clock_gettime(CLOCK_REALTIME,&abstime) != 0)
 216                                 PANIC("gc cannot get time");
 217
 218                         /*
 219                          * Do a backup poll in 10 seconds if no threads
 220                          * die before then.
 221                          */
 222                         abstime.tv_sec += 10;
 223
 224                         /*
 225                          * Wait for a signal from a dying thread or a
 226                          * timeout (for a backup poll).
 227                          */
 228                         if ((ret = pthread_cond_timedwait(&_gc_cond,
 229                             &_gc_mutex, &abstime)) != 0 && ret != ETIMEDOUT)
 230                                 PANIC("gc cannot wait for a signal");
 231                 }
 232
 233                 /* Unlock the garbage collector mutex: */
 234                 if (pthread_mutex_unlock(&_gc_mutex) != 0)
 235                         PANIC("Cannot unlock gc mutex");
 236
 237                 /*
 238                  * If there is memory to free, do it now. The call to
 239                  * free() might block, so this must be done outside the
 240                  * locks.
 241                  */
 242                 if (p_stack != NULL)
 243                         free(p_stack);
 244                 if (pthread_cln != NULL) {
 245                         if (pthread_cln->name != NULL) {
 246                                 /* Free the thread name string. */
 247                                 free(pthread_cln->name);
 248                         }
 249                         _rtld_free_tls(pthread_cln->tcb);
 250                         /*
 251                          * Free the memory allocated for the thread
 252                          * structure.
 253                          */
 254                         free(pthread_cln);
 255                 }
 256         }
 257         return (NULL);
 258 }