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