linuxthreads/join.c

   1 /* Linuxthreads - a simple clone()-based implementation of Posix        */
   2 /* threads for Linux.                                                   */
   3 /* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr)              */
   4 /*                                                                      */
   5 /* This program is free software; you can redistribute it and/or        */
   6 /* modify it under the terms of the GNU Library General Public License  */
   7 /* as published by the Free Software Foundation; either version 2       */
   8 /* of the License, or (at your option) any later version.               */
   9 /*                                                                      */
  10 /* This program is distributed in the hope that it will be useful,      */
  11 /* but WITHOUT ANY WARRANTY; without even the implied warranty of       */
  12 /* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the        */
  13 /* GNU Library General Public License for more details.                 */
  14
  15 /* Thread termination and joining */
  16
  17 #include <errno.h>
  18 #include <sched.h>
  19 #include <stdlib.h>
  20 #include <unistd.h>
  21 #include "pthread.h"
  22 #include "internals.h"
  23 #include "spinlock.h"
  24 #include "restart.h"
  25
  26 void pthread_exit(void * retval)
  27 {
  28   pthread_descr self = thread_self();
  29   pthread_descr joining;
  30   struct pthread_request request;
  31
  32   /* Reset the cancellation flag to avoid looping if the cleanup handlers
  33      contain cancellation points */
  34   THREAD_SETMEM(self, p_canceled, 0);
  35   /* Call cleanup functions and destroy the thread-specific data */
  36   __pthread_perform_cleanup();
  37   __pthread_destroy_specifics();
  38   /* Store return value */
  39   __pthread_lock(THREAD_GETMEM(self, p_lock), self);
  40   THREAD_SETMEM(self, p_retval, retval);
  41   /* See whether we have to signal the death.  */
  42   if (THREAD_GETMEM(self, p_report_events))
  43     {
  44       /* See whether TD_DEATH is in any of the mask.  */
  45       int idx = __td_eventword (TD_DEATH);
  46       uint32_t mask = __td_eventmask (TD_DEATH);
  47
  48       if ((mask & (__pthread_threads_events.event_bits[idx]
  49                    | THREAD_GETMEM_NC(self,
  50                                       p_eventbuf.eventmask.event_bits[idx])))
  51           != 0)
  52         {
  53           /* Yep, we have to signal the death.  */
  54           THREAD_SETMEM(self, p_eventbuf.eventnum, TD_DEATH);
  55           THREAD_SETMEM(self, p_eventbuf.eventdata, self);
  56           __pthread_last_event = self;
  57
  58           /* Now call the function to signal the event.  */
  59           __linuxthreads_death_event();
  60         }
  61     }
  62   /* Say that we've terminated */
  63   THREAD_SETMEM(self, p_terminated, 1);
  64   /* See if someone is joining on us */
  65   joining = THREAD_GETMEM(self, p_joining);
  66   __pthread_unlock(THREAD_GETMEM(self, p_lock));
  67   /* Restart joining thread if any */
  68   if (joining != NULL) restart(joining);
  69   /* If this is the initial thread, block until all threads have terminated.
  70      If another thread calls exit, we'll be terminated from our signal
  71      handler. */
  72   if (self == __pthread_main_thread && __pthread_manager_request >= 0) {
  73     request.req_thread = self;
  74     request.req_kind = REQ_MAIN_THREAD_EXIT;
  75     __libc_write(__pthread_manager_request, (char *)&request, sizeof(request));
  76     suspend(self);
  77     /* Main thread flushes stdio streams and runs atexit functions.
  78        It also calls a handler within LinuxThreads which sends a process exit
  79        request to the thread manager. */
  80     exit(0);
  81   }
  82   /* Threads other than the main one  terminate without flushing stdio streams
  83      or running atexit functions. */
  84   _exit(0);
  85 }
  86
  87 /* Function called by pthread_cancel to remove the thread from
  88    waiting on a condition variable queue. */
  89
  90 static int join_extricate_func(void *obj, pthread_descr th)
  91 {
  92   volatile pthread_descr self = thread_self();
  93   pthread_handle handle = obj;
  94   pthread_descr jo;
  95   int did_remove = 0;
  96
  97   __pthread_lock(&handle->h_lock, self);
  98   jo = handle->h_descr;
  99   did_remove = jo->p_joining != NULL;
 100   jo->p_joining = NULL;
 101   __pthread_unlock(&handle->h_lock);
 102
 103   return did_remove;
 104 }
 105
 106 int pthread_join(pthread_t thread_id, void ** thread_return)
 107 {
 108   volatile pthread_descr self = thread_self();
 109   struct pthread_request request;
 110   pthread_handle handle = thread_handle(thread_id);
 111   pthread_descr th;
 112   pthread_extricate_if extr;
 113   int already_canceled = 0;
 114
 115   /* Set up extrication interface */
 116   extr.pu_object = handle;
 117   extr.pu_extricate_func = join_extricate_func;
 118
 119   __pthread_lock(&handle->h_lock, self);
 120   if (nonexisting_handle(handle, thread_id)) {
 121     __pthread_unlock(&handle->h_lock);
 122     return ESRCH;
 123   }
 124   th = handle->h_descr;
 125   if (th == self) {
 126     __pthread_unlock(&handle->h_lock);
 127     return EDEADLK;
 128   }
 129   /* If detached or already joined, error */
 130   if (th->p_detached || th->p_joining != NULL) {
 131     __pthread_unlock(&handle->h_lock);
 132     return EINVAL;
 133   }
 134   /* If not terminated yet, suspend ourselves. */
 135   if (! th->p_terminated) {
 136     /* Register extrication interface */
 137     __pthread_set_own_extricate_if(self, &extr);
 138     if (!(THREAD_GETMEM(self, p_canceled)
 139         && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE))
 140       th->p_joining = self;
 141     else
 142       already_canceled = 1;
 143     __pthread_unlock(&handle->h_lock);
 144
 145     if (already_canceled) {
 146       __pthread_set_own_extricate_if(self, 0);
 147       pthread_exit(PTHREAD_CANCELED);
 148     }
 149
 150     suspend(self);
 151     /* Deregister extrication interface */
 152     __pthread_set_own_extricate_if(self, 0);
 153
 154     /* This is a cancellation point */
 155     if (THREAD_GETMEM(self, p_woken_by_cancel)
 156         && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) {
 157       THREAD_SETMEM(self, p_woken_by_cancel, 0);
 158       pthread_exit(PTHREAD_CANCELED);
 159     }
 160     __pthread_lock(&handle->h_lock, self);
 161   }
 162   /* Get return value */
 163   if (thread_return != NULL) *thread_return = th->p_retval;
 164   __pthread_unlock(&handle->h_lock);
 165   /* Send notification to thread manager */
 166   if (__pthread_manager_request >= 0) {
 167     request.req_thread = self;
 168     request.req_kind = REQ_FREE;
 169     request.req_args.free.thread_id = thread_id;
 170     __libc_write(__pthread_manager_request,
 171                  (char *) &request, sizeof(request));
 172   }
 173   return 0;
 174 }
 175
 176 int pthread_detach(pthread_t thread_id)
 177 {
 178   int terminated;
 179   struct pthread_request request;
 180   pthread_handle handle = thread_handle(thread_id);
 181   pthread_descr th;
 182
 183   __pthread_lock(&handle->h_lock, NULL);
 184   if (invalid_handle(handle, thread_id)) {
 185     __pthread_unlock(&handle->h_lock);
 186     return ESRCH;
 187   }
 188   th = handle->h_descr;
 189   /* If already detached, error */
 190   if (th->p_detached) {
 191     __pthread_unlock(&handle->h_lock);
 192     return EINVAL;
 193   }
 194   /* If already joining, don't do anything. */
 195   if (th->p_joining != NULL) {
 196     __pthread_unlock(&handle->h_lock);
 197     return 0;
 198   }
 199   /* Mark as detached */
 200   th->p_detached = 1;
 201   terminated = th->p_terminated;
 202   __pthread_unlock(&handle->h_lock);
 203   /* If already terminated, notify thread manager to reclaim resources */
 204   if (terminated && __pthread_manager_request >= 0) {
 205     request.req_thread = thread_self();
 206     request.req_kind = REQ_FREE;
 207     request.req_args.free.thread_id = thread_id;
 208     __libc_write(__pthread_manager_request,
 209                  (char *) &request, sizeof(request));
 210   }
 211   return 0;
 212 }