nptl/sysdeps/pthread/createthread.c

   1 /* Copyright (C) 2002-2013 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, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <sched.h>
  20 #include <setjmp.h>
  21 #include <signal.h>
  22 #include <stdlib.h>
  23 #include <atomic.h>
  24 #include <ldsodefs.h>
  25 #include <tls.h>
  26
  27 #include "kernel-features.h"
  28
  29
  30 #define CLONE_SIGNAL            (CLONE_SIGHAND | CLONE_THREAD)
  31
  32 /* Unless otherwise specified, the thread "register" is going to be
  33    initialized with a pointer to the TCB.  */
  34 #ifndef TLS_VALUE
  35 # define TLS_VALUE pd
  36 #endif
  37
  38 #ifndef ARCH_CLONE
  39 # define ARCH_CLONE __clone
  40 #endif
  41
  42
  43 #ifndef TLS_MULTIPLE_THREADS_IN_TCB
  44 /* Pointer to the corresponding variable in libc.  */
  45 int *__libc_multiple_threads_ptr attribute_hidden;
  46 #endif
  47
  48
  49 static int
  50 do_clone (struct pthread *pd, const struct pthread_attr *attr,
  51           int clone_flags, int (*fct) (void *), STACK_VARIABLES_PARMS,
  52           int stopped)
  53 {
  54 #ifdef PREPARE_CREATE
  55   PREPARE_CREATE;
  56 #endif
  57
  58   if (__builtin_expect (stopped != 0, 0))
  59     /* We make sure the thread does not run far by forcing it to get a
  60        lock.  We lock it here too so that the new thread cannot continue
  61        until we tell it to.  */
  62     lll_lock (pd->lock, LLL_PRIVATE);
  63
  64   /* One more thread.  We cannot have the thread do this itself, since it
  65      might exist but not have been scheduled yet by the time we've returned
  66      and need to check the value to behave correctly.  We must do it before
  67      creating the thread, in case it does get scheduled first and then
  68      might mistakenly think it was the only thread.  In the failure case,
  69      we momentarily store a false value; this doesn't matter because there
  70      is no kosher thing a signal handler interrupting us right here can do
  71      that cares whether the thread count is correct.  */
  72   atomic_increment (&__nptl_nthreads);
  73
  74   int rc = ARCH_CLONE (fct, STACK_VARIABLES_ARGS, clone_flags,
  75                        pd, &pd->tid, TLS_VALUE, &pd->tid);
  76
  77   if (__builtin_expect (rc == -1, 0))
  78     {
  79       atomic_decrement (&__nptl_nthreads); /* Oops, we lied for a second.  */
  80
  81       /* Perhaps a thread wants to change the IDs and if waiting
  82          for this stillborn thread.  */
  83       if (__builtin_expect (atomic_exchange_acq (&pd->setxid_futex, 0)
  84                             == -2, 0))
  85         lll_futex_wake (&pd->setxid_futex, 1, LLL_PRIVATE);
  86
  87       /* Free the resources.  */
  88         __deallocate_stack (pd);
  89
  90       /* We have to translate error codes.  */
  91       return errno == ENOMEM ? EAGAIN : errno;
  92     }
  93
  94   /* Now we have the possibility to set scheduling parameters etc.  */
  95   if (__builtin_expect (stopped != 0, 0))
  96     {
  97       INTERNAL_SYSCALL_DECL (err);
  98       int res = 0;
  99
 100       /* Set the affinity mask if necessary.  */
 101       if (attr->cpuset != NULL)
 102         {
 103           res = INTERNAL_SYSCALL (sched_setaffinity, err, 3, pd->tid,
 104                                   attr->cpusetsize, attr->cpuset);
 105
 106           if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (res, err), 0))
 107             {
 108               /* The operation failed.  We have to kill the thread.  First
 109                  send it the cancellation signal.  */
 110               INTERNAL_SYSCALL_DECL (err2);
 111             err_out:
 112               (void) INTERNAL_SYSCALL (tgkill, err2, 3,
 113                                        THREAD_GETMEM (THREAD_SELF, pid),
 114                                        pd->tid, SIGCANCEL);
 115
 116               /* We do not free the stack here because the canceled thread
 117                  itself will do this.  */
 118
 119               return (INTERNAL_SYSCALL_ERROR_P (res, err)
 120                       ? INTERNAL_SYSCALL_ERRNO (res, err)
 121                       : 0);
 122             }
 123         }
 124
 125       /* Set the scheduling parameters.  */
 126       if ((attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0)
 127         {
 128           res = INTERNAL_SYSCALL (sched_setscheduler, err, 3, pd->tid,
 129                                   pd->schedpolicy, &pd->schedparam);
 130
 131           if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (res, err), 0))
 132             goto err_out;
 133         }
 134     }
 135
 136   /* We now have for sure more than one thread.  The main thread might
 137      not yet have the flag set.  No need to set the global variable
 138      again if this is what we use.  */
 139   THREAD_SETMEM (THREAD_SELF, header.multiple_threads, 1);
 140
 141   return 0;
 142 }
 143
 144
 145 static int
 146 create_thread (struct pthread *pd, const struct pthread_attr *attr,
 147                STACK_VARIABLES_PARMS)
 148 {
 149 #ifdef TLS_TCB_AT_TP
 150   assert (pd->header.tcb != NULL);
 151 #endif
 152
 153   /* We rely heavily on various flags the CLONE function understands:
 154
 155      CLONE_VM, CLONE_FS, CLONE_FILES
 156         These flags select semantics with shared address space and
 157         file descriptors according to what POSIX requires.
 158
 159      CLONE_SIGNAL
 160         This flag selects the POSIX signal semantics.
 161
 162      CLONE_SETTLS
 163         The sixth parameter to CLONE determines the TLS area for the
 164         new thread.
 165
 166      CLONE_PARENT_SETTID
 167         The kernels writes the thread ID of the newly created thread
 168         into the location pointed to by the fifth parameters to CLONE.
 169
 170         Note that it would be semantically equivalent to use
 171         CLONE_CHILD_SETTID but it is be more expensive in the kernel.
 172
 173      CLONE_CHILD_CLEARTID
 174         The kernels clears the thread ID of a thread that has called
 175         sys_exit() in the location pointed to by the seventh parameter
 176         to CLONE.
 177
 178      The termination signal is chosen to be zero which means no signal
 179      is sent.  */
 180   int clone_flags = (CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGNAL
 181                      | CLONE_SETTLS | CLONE_PARENT_SETTID
 182                      | CLONE_CHILD_CLEARTID | CLONE_SYSVSEM
 183                      | 0);
 184
 185   if (__builtin_expect (THREAD_GETMEM (THREAD_SELF, report_events), 0))
 186     {
 187       /* The parent thread is supposed to report events.  Check whether
 188          the TD_CREATE event is needed, too.  */
 189       const int _idx = __td_eventword (TD_CREATE);
 190       const uint32_t _mask = __td_eventmask (TD_CREATE);
 191
 192       if ((_mask & (__nptl_threads_events.event_bits[_idx]
 193                     | pd->eventbuf.eventmask.event_bits[_idx])) != 0)
 194         {
 195           /* We always must have the thread start stopped.  */
 196           pd->stopped_start = true;
 197
 198           /* Create the thread.  We always create the thread stopped
 199              so that it does not get far before we tell the debugger.  */
 200           int res = do_clone (pd, attr, clone_flags, start_thread,
 201                               STACK_VARIABLES_ARGS, 1);
 202           if (res == 0)
 203             {
 204               /* Now fill in the information about the new thread in
 205                  the newly created thread's data structure.  We cannot let
 206                  the new thread do this since we don't know whether it was
 207                  already scheduled when we send the event.  */
 208               pd->eventbuf.eventnum = TD_CREATE;
 209               pd->eventbuf.eventdata = pd;
 210
 211               /* Enqueue the descriptor.  */
 212               do
 213                 pd->nextevent = __nptl_last_event;
 214               while (atomic_compare_and_exchange_bool_acq (&__nptl_last_event,
 215                                                            pd, pd->nextevent)
 216                      != 0);
 217
 218               /* Now call the function which signals the event.  */
 219               __nptl_create_event ();
 220
 221               /* And finally restart the new thread.  */
 222               lll_unlock (pd->lock, LLL_PRIVATE);
 223             }
 224
 225           return res;
 226         }
 227     }
 228
 229 #ifdef NEED_DL_SYSINFO
 230   assert (THREAD_SELF_SYSINFO == THREAD_SYSINFO (pd));
 231 #endif
 232
 233   /* Determine whether the newly created threads has to be started
 234      stopped since we have to set the scheduling parameters or set the
 235      affinity.  */
 236   bool stopped = false;
 237   if (attr != NULL && (attr->cpuset != NULL
 238                        || (attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0))
 239     stopped = true;
 240   pd->stopped_start = stopped;
 241   pd->parent_cancelhandling = THREAD_GETMEM (THREAD_SELF, cancelhandling);
 242
 243   /* Actually create the thread.  */
 244   int res = do_clone (pd, attr, clone_flags, start_thread,
 245                       STACK_VARIABLES_ARGS, stopped);
 246
 247   if (res == 0 && stopped)
 248     /* And finally restart the new thread.  */
 249     lll_unlock (pd->lock, LLL_PRIVATE);
 250
 251   return res;
 252 }