nptl/sysdeps/pthread/createthread.c

   1 /* Copyright (C) 2002, 2003, 2004 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 /* Variable set to a nonzero value if more than one thread runs or ran.  */
  46 int __pthread_multiple_threads attribute_hidden;
  47 /* Pointer to the corresponding variable in libc.  */
  48 int *__libc_multiple_threads_ptr attribute_hidden;
  49 #endif
  50
  51
  52 static int
  53 do_clone (struct pthread *pd, const struct pthread_attr *attr,
  54           int clone_flags, int (*fct) (void *), STACK_VARIABLES_PARMS,
  55           int stopped)
  56 {
  57 #ifdef PREPARE_CREATE
  58   PREPARE_CREATE;
  59 #endif
  60
  61   if (stopped)
  62     /* We Make sure the thread does not run far by forcing it to get a
  63        lock.  We lock it here too so that the new thread cannot continue
  64        until we tell it to.  */
  65     lll_lock (pd->lock);
  66
  67   /* One more thread.  We cannot have the thread do this itself, since it
  68      might exist but not have been scheduled yet by the time we've returned
  69      and need to check the value to behave correctly.  We must do it before
  70      creating the thread, in case it does get scheduled first and then
  71      might mistakenly think it was the only thread.  In the failure case,
  72      we momentarily store a false value; this doesn't matter because there
  73      is no kosher thing a signal handler interrupting us right here can do
  74      that cares whether the thread count is correct.  */
  75   atomic_increment (&__nptl_nthreads);
  76
  77   if (ARCH_CLONE (fct, STACK_VARIABLES_ARGS, clone_flags,
  78                   pd, &pd->tid, TLS_VALUE, &pd->tid) == -1)
  79     {
  80       atomic_decrement (&__nptl_nthreads); /* Oops, we lied for a second.  */
  81
  82       /* Failed.  If the thread is detached, remove the TCB here since
  83          the caller cannot do this.  The caller remembered the thread
  84          as detached and cannot reverify that it is not since it must
  85          not access the thread descriptor again.  */
  86       if (IS_DETACHED (pd))
  87         __deallocate_stack (pd);
  88
  89       return errno;
  90     }
  91
  92   /* Now we have the possibility to set scheduling parameters etc.  */
  93   if (__builtin_expect (stopped != 0, 0))
  94     {
  95       INTERNAL_SYSCALL_DECL (err);
  96       int res = 0;
  97
  98       /* Set the affinity mask if necessary.  */
  99       if (attr->cpuset != NULL)
 100         {
 101           res = INTERNAL_SYSCALL (sched_setaffinity, err, 3, pd->tid,
 102                                   sizeof (cpu_set_t), attr->cpuset);
 103
 104           if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (res, err), 0))
 105             {
 106               /* The operation failed.  We have to kill the thread.  First
 107                  send it the cancellation signal.  */
 108               INTERNAL_SYSCALL_DECL (err2);
 109             err_out:
 110 #if __ASSUME_TGKILL
 111               (void) INTERNAL_SYSCALL (tgkill, err2, 3,
 112                                        THREAD_GETMEM (THREAD_SELF, pid),
 113                                        pd->tid, SIGCANCEL);
 114 #else
 115               (void) INTERNAL_SYSCALL (tkill, err2, 2, pd->tid, SIGCANCEL);
 116 #endif
 117
 118               return (INTERNAL_SYSCALL_ERROR_P (res, err)
 119                       ? INTERNAL_SYSCALL_ERRNO (res, err)
 120                       : 0);
 121             }
 122         }
 123
 124       /* Set the scheduling parameters.  */
 125       if ((attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0)
 126         {
 127           res = INTERNAL_SYSCALL (sched_setscheduler, err, 3, pd->tid,
 128                                   pd->schedpolicy, &pd->schedparam);
 129
 130           if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (res, err), 0))
 131             goto err_out;
 132         }
 133     }
 134
 135   /* We now have for sure more than one thread.  The main thread might
 136      not yet have the flag set.  No need to set the global variable
 137      again if this is what we use.  */
 138   THREAD_SETMEM (THREAD_SELF, header.multiple_threads, 1);
 139
 140   return 0;
 141 }
 142
 143
 144 static int
 145 create_thread (struct pthread *pd, const struct pthread_attr *attr,
 146                STACK_VARIABLES_PARMS)
 147 {
 148 #ifdef TLS_TCB_AT_TP
 149   assert (pd->header.tcb != NULL);
 150 #endif
 151
 152   /* We rely heavily on various flags the CLONE function understands:
 153
 154      CLONE_VM, CLONE_FS, CLONE_FILES
 155         These flags select semantics with shared address space and
 156         file descriptors according to what POSIX requires.
 157
 158      CLONE_SIGNAL
 159         This flag selects the POSIX signal semantics.
 160
 161      CLONE_SETTLS
 162         The sixth parameter to CLONE determines the TLS area for the
 163         new thread.
 164
 165      CLONE_PARENT_SETTID
 166         The kernels writes the thread ID of the newly created thread
 167         into the location pointed to by the fifth parameters to CLONE.
 168
 169         Note that it would be semantically equivalent to use
 170         CLONE_CHILD_SETTID but it is be more expensive in the kernel.
 171
 172      CLONE_CHILD_CLEARTID
 173         The kernels clears the thread ID of a thread that has called
 174         sys_exit() in the location pointed to by the seventh parameter
 175         to CLONE.
 176
 177      CLONE_DETACHED
 178         No signal is generated if the thread exists and it is
 179         automatically reaped.
 180
 181      The termination signal is chosen to be zero which means no signal
 182      is sent.  */
 183   int clone_flags = (CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGNAL
 184                      | CLONE_SETTLS | CLONE_PARENT_SETTID
 185                      | CLONE_CHILD_CLEARTID | CLONE_SYSVSEM
 186 #if __ASSUME_NO_CLONE_DETACHED == 0
 187                      | CLONE_DETACHED
 188 #endif
 189                      | 0);
 190
 191   if (__builtin_expect (THREAD_GETMEM (THREAD_SELF, report_events), 0))
 192     {
 193       /* The parent thread is supposed to report events.  Check whether
 194          the TD_CREATE event is needed, too.  */
 195       const int _idx = __td_eventword (TD_CREATE);
 196       const uint32_t _mask = __td_eventmask (TD_CREATE);
 197
 198       if ((_mask & (__nptl_threads_events.event_bits[_idx]
 199                     | pd->eventbuf.eventmask.event_bits[_idx])) != 0)
 200         {
 201           /* We always must have the thread start stopped.  */
 202           pd->stopped_start = true;
 203
 204           /* Create the thread.  We always create the thread stopped
 205              so that it does not get far before we tell the debugger.  */
 206           int res = do_clone (pd, attr, clone_flags, start_thread,
 207                               STACK_VARIABLES_ARGS, 1);
 208           if (res == 0)
 209             {
 210               /* Now fill in the information about the new thread in
 211                  the newly created thread's data structure.  We cannot let
 212                  the new thread do this since we don't know whether it was
 213                  already scheduled when we send the event.  */
 214               pd->eventbuf.eventnum = TD_CREATE;
 215               pd->eventbuf.eventdata = pd;
 216
 217               /* Enqueue the descriptor.  */
 218               do
 219                 pd->nextevent = __nptl_last_event;
 220               while (atomic_compare_and_exchange_bool_acq (&__nptl_last_event,
 221                                                            pd, pd->nextevent)
 222                      != 0);
 223
 224               /* Now call the function which signals the event.  */
 225               __nptl_create_event ();
 226
 227               /* And finally restart the new thread.  */
 228               lll_unlock (pd->lock);
 229             }
 230
 231           return res;
 232         }
 233     }
 234
 235 #ifdef NEED_DL_SYSINFO
 236   assert (THREAD_SELF_SYSINFO == THREAD_SYSINFO (pd));
 237 #endif
 238
 239   /* Determine whether the newly created threads has to be started
 240      stopped since we have to set the scheduling parameters or set the
 241      affinity.  */
 242   bool stopped = false;
 243   if (attr != NULL && (attr->cpuset != NULL
 244                        || (attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0))
 245     stopped = true;
 246   pd->stopped_start = stopped;
 247
 248   /* Actually create the thread.  */
 249   int res = do_clone (pd, attr, clone_flags, start_thread,
 250                       STACK_VARIABLES_ARGS, stopped);
 251
 252   if (res == 0 && stopped)
 253     /* And finally restart the new thread.  */
 254     lll_unlock (pd->lock);
 255
 256   return res;
 257 }