nptl/sysdeps/pthread/createthread.c

   1 /* Copyright (C) 2002-2007, 2008 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   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       /* We have to translate error codes.  */
  88       return errno == ENOMEM ? EAGAIN : errno;
  89     }
  90
  91   /* Now we have the possibility to set scheduling parameters etc.  */
  92   if (__builtin_expect (stopped != 0, 0))
  93     {
  94       INTERNAL_SYSCALL_DECL (err);
  95       int res = 0;
  96
  97       /* Set the affinity mask if necessary.  */
  98       if (attr->cpuset != NULL)
  99         {
 100           res = INTERNAL_SYSCALL (sched_setaffinity, err, 3, pd->tid,
 101                                   attr->cpusetsize, attr->cpuset);
 102
 103           if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (res, err), 0))
 104             {
 105               /* The operation failed.  We have to kill the thread.  First
 106                  send it the cancellation signal.  */
 107               INTERNAL_SYSCALL_DECL (err2);
 108             err_out:
 109 #if __ASSUME_TGKILL
 110               (void) INTERNAL_SYSCALL (tgkill, err2, 3,
 111                                        THREAD_GETMEM (THREAD_SELF, pid),
 112                                        pd->tid, SIGCANCEL);
 113 #else
 114               (void) INTERNAL_SYSCALL (tkill, err2, 2, pd->tid, SIGCANCEL);
 115 #endif
 116
 117               return (INTERNAL_SYSCALL_ERROR_P (res, err)
 118                       ? INTERNAL_SYSCALL_ERRNO (res, err)
 119                       : 0);
 120             }
 121         }
 122
 123       /* Set the scheduling parameters.  */
 124       if ((attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0)
 125         {
 126           res = INTERNAL_SYSCALL (sched_setscheduler, err, 3, pd->tid,
 127                                   pd->schedpolicy, &pd->schedparam);
 128
 129           if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (res, err), 0))
 130             goto err_out;
 131         }
 132     }
 133
 134   /* We now have for sure more than one thread.  The main thread might
 135      not yet have the flag set.  No need to set the global variable
 136      again if this is what we use.  */
 137   THREAD_SETMEM (THREAD_SELF, header.multiple_threads, 1);
 138
 139   return 0;
 140 }
 141
 142
 143 static int
 144 create_thread (struct pthread *pd, const struct pthread_attr *attr,
 145                STACK_VARIABLES_PARMS)
 146 {
 147 #ifdef TLS_TCB_AT_TP
 148   assert (pd->header.tcb != NULL);
 149 #endif
 150
 151   /* We rely heavily on various flags the CLONE function understands:
 152
 153      CLONE_VM, CLONE_FS, CLONE_FILES
 154         These flags select semantics with shared address space and
 155         file descriptors according to what POSIX requires.
 156
 157      CLONE_SIGNAL
 158         This flag selects the POSIX signal semantics.
 159
 160      CLONE_SETTLS
 161         The sixth parameter to CLONE determines the TLS area for the
 162         new thread.
 163
 164      CLONE_PARENT_SETTID
 165         The kernels writes the thread ID of the newly created thread
 166         into the location pointed to by the fifth parameters to CLONE.
 167
 168         Note that it would be semantically equivalent to use
 169         CLONE_CHILD_SETTID but it is be more expensive in the kernel.
 170
 171      CLONE_CHILD_CLEARTID
 172         The kernels clears the thread ID of a thread that has called
 173         sys_exit() in the location pointed to by the seventh parameter
 174         to CLONE.
 175
 176      CLONE_DETACHED
 177         No signal is generated if the thread exists and it is
 178         automatically reaped.
 179
 180      The termination signal is chosen to be zero which means no signal
 181      is sent.  */
 182   int clone_flags = (CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGNAL
 183                      | CLONE_SETTLS | CLONE_PARENT_SETTID
 184                      | CLONE_CHILD_CLEARTID | CLONE_SYSVSEM
 185 #if __ASSUME_NO_CLONE_DETACHED == 0
 186                      | CLONE_DETACHED
 187 #endif
 188                      | 0);
 189
 190   if (__builtin_expect (THREAD_GETMEM (THREAD_SELF, report_events), 0))
 191     {
 192       /* The parent thread is supposed to report events.  Check whether
 193          the TD_CREATE event is needed, too.  */
 194       const int _idx = __td_eventword (TD_CREATE);
 195       const uint32_t _mask = __td_eventmask (TD_CREATE);
 196
 197       if ((_mask & (__nptl_threads_events.event_bits[_idx]
 198                     | pd->eventbuf.eventmask.event_bits[_idx])) != 0)
 199         {
 200           /* We always must have the thread start stopped.  */
 201           pd->stopped_start = true;
 202
 203           /* Create the thread.  We always create the thread stopped
 204              so that it does not get far before we tell the debugger.  */
 205           int res = do_clone (pd, attr, clone_flags, start_thread,
 206                               STACK_VARIABLES_ARGS, 1);
 207           if (res == 0)
 208             {
 209               /* Now fill in the information about the new thread in
 210                  the newly created thread's data structure.  We cannot let
 211                  the new thread do this since we don't know whether it was
 212                  already scheduled when we send the event.  */
 213               pd->eventbuf.eventnum = TD_CREATE;
 214               pd->eventbuf.eventdata = pd;
 215
 216               /* Enqueue the descriptor.  */
 217               do
 218                 pd->nextevent = __nptl_last_event;
 219               while (atomic_compare_and_exchange_bool_acq (&__nptl_last_event,
 220                                                            pd, pd->nextevent)
 221                      != 0);
 222
 223               /* Now call the function which signals the event.  */
 224               __nptl_create_event ();
 225
 226               /* And finally restart the new thread.  */
 227               lll_unlock (pd->lock, LLL_PRIVATE);
 228             }
 229
 230           return res;
 231         }
 232     }
 233
 234 #ifdef NEED_DL_SYSINFO
 235   assert (THREAD_SELF_SYSINFO == THREAD_SYSINFO (pd));
 236 #endif
 237
 238   /* Determine whether the newly created threads has to be started
 239      stopped since we have to set the scheduling parameters or set the
 240      affinity.  */
 241   bool stopped = false;
 242   if (attr != NULL && (attr->cpuset != NULL
 243                        || (attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0))
 244     stopped = true;
 245   pd->stopped_start = stopped;
 246   pd->parent_cancelhandling = THREAD_GETMEM (THREAD_SELF, cancelhandling);
 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, LLL_PRIVATE);
 255
 256   return res;
 257 }