nptl/sysdeps/pthread/createthread.c

   1 /* Copyright (C) 2002-2007, 2008, 2010 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library 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 GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <sched.h>
  21 #include <setjmp.h>
  22 #include <signal.h>
  23 #include <stdlib.h>
  24 #include <atomic.h>
  25 #include <ldsodefs.h>
  26 #include <tls.h>
  27
  28 #include "kernel-features.h"
  29
  30
  31 #define CLONE_SIGNAL            (CLONE_SIGHAND | CLONE_THREAD)
  32
  33 /* Unless otherwise specified, the thread "register" is going to be
  34    initialized with a pointer to the TCB.  */
  35 #ifndef TLS_VALUE
  36 # define TLS_VALUE pd
  37 #endif
  38
  39 #ifndef ARCH_CLONE
  40 # define ARCH_CLONE __clone
  41 #endif
  42
  43
  44 #ifndef TLS_MULTIPLE_THREADS_IN_TCB
  45 /* Pointer to the corresponding variable in libc.  */
  46 int *__libc_multiple_threads_ptr attribute_hidden;
  47 #endif
  48
  49
  50 static int
  51 do_clone (struct pthread *pd, const struct pthread_attr *attr,
  52           int clone_flags, int (*fct) (void *), STACK_VARIABLES_PARMS,
  53           int stopped)
  54 {
  55 #ifdef PREPARE_CREATE
  56   PREPARE_CREATE;
  57 #endif
  58
  59   if (__builtin_expect (stopped != 0, 0))
  60     /* We make sure the thread does not run far by forcing it to get a
  61        lock.  We lock it here too so that the new thread cannot continue
  62        until we tell it to.  */
  63     lll_lock (pd->lock, LLL_PRIVATE);
  64
  65   /* One more thread.  We cannot have the thread do this itself, since it
  66      might exist but not have been scheduled yet by the time we've returned
  67      and need to check the value to behave correctly.  We must do it before
  68      creating the thread, in case it does get scheduled first and then
  69      might mistakenly think it was the only thread.  In the failure case,
  70      we momentarily store a false value; this doesn't matter because there
  71      is no kosher thing a signal handler interrupting us right here can do
  72      that cares whether the thread count is correct.  */
  73   atomic_increment (&__nptl_nthreads);
  74
  75   int rc = ARCH_CLONE (fct, STACK_VARIABLES_ARGS, clone_flags,
  76                        pd, &pd->tid, TLS_VALUE, &pd->tid);
  77
  78   if (__builtin_expect (rc == -1, 0))
  79     {
  80       atomic_decrement (&__nptl_nthreads); /* Oops, we lied for a second.  */
  81
  82       /* Perhaps a thread wants to change the IDs and if waiting
  83          for this stillborn thread.  */
  84       if (__builtin_expect (atomic_exchange_acq (&pd->setxid_futex, 0)
  85                             == -2, 0))
  86         lll_futex_wake (&pd->setxid_futex, 1, LLL_PRIVATE);
  87
  88       /* Free the resources.  */
  89         __deallocate_stack (pd);
  90
  91       /* We have to translate error codes.  */
  92       return errno == ENOMEM ? EAGAIN : errno;
  93     }
  94
  95   /* Now we have the possibility to set scheduling parameters etc.  */
  96   if (__builtin_expect (stopped != 0, 0))
  97     {
  98       INTERNAL_SYSCALL_DECL (err);
  99       int res = 0;
 100
 101       /* Set the affinity mask if necessary.  */
 102       if (attr->cpuset != NULL)
 103         {
 104           res = INTERNAL_SYSCALL (sched_setaffinity, err, 3, pd->tid,
 105                                   attr->cpusetsize, attr->cpuset);
 106
 107           if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (res, err), 0))
 108             {
 109               /* The operation failed.  We have to kill the thread.  First
 110                  send it the cancellation signal.  */
 111               INTERNAL_SYSCALL_DECL (err2);
 112             err_out:
 113 #if __ASSUME_TGKILL
 114               (void) INTERNAL_SYSCALL (tgkill, err2, 3,
 115                                        THREAD_GETMEM (THREAD_SELF, pid),
 116                                        pd->tid, SIGCANCEL);
 117 #else
 118               (void) INTERNAL_SYSCALL (tkill, err2, 2, pd->tid, SIGCANCEL);
 119 #endif
 120
 121               /* We do not free the stack here because the canceled thread
 122                  itself will do this.  */
 123
 124               return (INTERNAL_SYSCALL_ERROR_P (res, err)
 125                       ? INTERNAL_SYSCALL_ERRNO (res, err)
 126                       : 0);
 127             }
 128         }
 129
 130       /* Set the scheduling parameters.  */
 131       if ((attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0)
 132         {
 133           res = INTERNAL_SYSCALL (sched_setscheduler, err, 3, pd->tid,
 134                                   pd->schedpolicy, &pd->schedparam);
 135
 136           if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (res, err), 0))
 137             goto err_out;
 138         }
 139     }
 140
 141   /* We now have for sure more than one thread.  The main thread might
 142      not yet have the flag set.  No need to set the global variable
 143      again if this is what we use.  */
 144   THREAD_SETMEM (THREAD_SELF, header.multiple_threads, 1);
 145
 146   return 0;
 147 }
 148
 149
 150 static int
 151 create_thread (struct pthread *pd, const struct pthread_attr *attr,
 152                STACK_VARIABLES_PARMS)
 153 {
 154 #ifdef TLS_TCB_AT_TP
 155   assert (pd->header.tcb != NULL);
 156 #endif
 157
 158   /* We rely heavily on various flags the CLONE function understands:
 159
 160      CLONE_VM, CLONE_FS, CLONE_FILES
 161         These flags select semantics with shared address space and
 162         file descriptors according to what POSIX requires.
 163
 164      CLONE_SIGNAL
 165         This flag selects the POSIX signal semantics.
 166
 167      CLONE_SETTLS
 168         The sixth parameter to CLONE determines the TLS area for the
 169         new thread.
 170
 171      CLONE_PARENT_SETTID
 172         The kernels writes the thread ID of the newly created thread
 173         into the location pointed to by the fifth parameters to CLONE.
 174
 175         Note that it would be semantically equivalent to use
 176         CLONE_CHILD_SETTID but it is be more expensive in the kernel.
 177
 178      CLONE_CHILD_CLEARTID
 179         The kernels clears the thread ID of a thread that has called
 180         sys_exit() in the location pointed to by the seventh parameter
 181         to CLONE.
 182
 183      CLONE_DETACHED
 184         No signal is generated if the thread exists and it is
 185         automatically reaped.
 186
 187      The termination signal is chosen to be zero which means no signal
 188      is sent.  */
 189   int clone_flags = (CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGNAL
 190                      | CLONE_SETTLS | CLONE_PARENT_SETTID
 191                      | CLONE_CHILD_CLEARTID | CLONE_SYSVSEM
 192 #if __ASSUME_NO_CLONE_DETACHED == 0
 193                      | CLONE_DETACHED
 194 #endif
 195                      | 0);
 196
 197   if (__builtin_expect (THREAD_GETMEM (THREAD_SELF, report_events), 0))
 198     {
 199       /* The parent thread is supposed to report events.  Check whether
 200          the TD_CREATE event is needed, too.  */
 201       const int _idx = __td_eventword (TD_CREATE);
 202       const uint32_t _mask = __td_eventmask (TD_CREATE);
 203
 204       if ((_mask & (__nptl_threads_events.event_bits[_idx]
 205                     | pd->eventbuf.eventmask.event_bits[_idx])) != 0)
 206         {
 207           /* We always must have the thread start stopped.  */
 208           pd->stopped_start = true;
 209
 210           /* Create the thread.  We always create the thread stopped
 211              so that it does not get far before we tell the debugger.  */
 212           int res = do_clone (pd, attr, clone_flags, start_thread,
 213                               STACK_VARIABLES_ARGS, 1);
 214           if (res == 0)
 215             {
 216               /* Now fill in the information about the new thread in
 217                  the newly created thread's data structure.  We cannot let
 218                  the new thread do this since we don't know whether it was
 219                  already scheduled when we send the event.  */
 220               pd->eventbuf.eventnum = TD_CREATE;
 221               pd->eventbuf.eventdata = pd;
 222
 223               /* Enqueue the descriptor.  */
 224               do
 225                 pd->nextevent = __nptl_last_event;
 226               while (atomic_compare_and_exchange_bool_acq (&__nptl_last_event,
 227                                                            pd, pd->nextevent)
 228                      != 0);
 229
 230               /* Now call the function which signals the event.  */
 231               __nptl_create_event ();
 232
 233               /* And finally restart the new thread.  */
 234               lll_unlock (pd->lock, LLL_PRIVATE);
 235             }
 236
 237           return res;
 238         }
 239     }
 240
 241 #ifdef NEED_DL_SYSINFO
 242   assert (THREAD_SELF_SYSINFO == THREAD_SYSINFO (pd));
 243 #endif
 244
 245   /* Determine whether the newly created threads has to be started
 246      stopped since we have to set the scheduling parameters or set the
 247      affinity.  */
 248   bool stopped = false;
 249   if (attr != NULL && (attr->cpuset != NULL
 250                        || (attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0))
 251     stopped = true;
 252   pd->stopped_start = stopped;
 253   pd->parent_cancelhandling = THREAD_GETMEM (THREAD_SELF, cancelhandling);
 254
 255   /* Actually create the thread.  */
 256   int res = do_clone (pd, attr, clone_flags, start_thread,
 257                       STACK_VARIABLES_ARGS, stopped);
 258
 259   if (res == 0 && stopped)
 260     /* And finally restart the new thread.  */
 261     lll_unlock (pd->lock, LLL_PRIVATE);
 262
 263   return res;
 264 }