sysdeps/unix/sysv/linux/createthread.c

   1 /* Low-level thread creation for NPTL.  Linux version.
   2    Copyright (C) 2002-2021 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <https://www.gnu.org/licenses/>.  */
  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 #include <stdint.h>
  28
  29 #include <arch-fork.h>
  30
  31 #ifdef __NR_clone2
  32 # define ARCH_CLONE __clone2
  33 #else
  34 # define ARCH_CLONE __clone
  35 #endif
  36
  37 /* See the comments in pthread_create.c for the requirements for these
  38    two macros and the create_thread function.  */
  39
  40 #define START_THREAD_DEFN \
  41   static int __attribute__ ((noreturn)) start_thread (void *arg)
  42 #define START_THREAD_SELF arg
  43
  44 /* pthread_create.c defines this using START_THREAD_DEFN
  45    We need a forward declaration here so we can take its address.  */
  46 static int start_thread (void *arg) __attribute__ ((noreturn));
  47
  48 static int
  49 create_thread (struct pthread *pd, const struct pthread_attr *attr,
  50                bool *stopped_start, STACK_VARIABLES_PARMS, bool *thread_ran)
  51 {
  52   /* Determine whether the newly created threads has to be started
  53      stopped since we have to set the scheduling parameters or set the
  54      affinity.  */
  55   bool need_setaffinity = (attr != NULL && attr->extension != NULL
  56                            && attr->extension->cpuset != 0);
  57   if (attr != NULL
  58       && (__glibc_unlikely (need_setaffinity)
  59           || __glibc_unlikely ((attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0)))
  60     *stopped_start = true;
  61
  62   pd->stopped_start = *stopped_start;
  63   if (__glibc_unlikely (*stopped_start))
  64     /* See CONCURRENCY NOTES in nptl/pthread_creat.c.  */
  65     lll_lock (pd->lock, LLL_PRIVATE);
  66
  67   /* We rely heavily on various flags the CLONE function understands:
  68
  69      CLONE_VM, CLONE_FS, CLONE_FILES
  70         These flags select semantics with shared address space and
  71         file descriptors according to what POSIX requires.
  72
  73      CLONE_SIGHAND, CLONE_THREAD
  74         This flag selects the POSIX signal semantics and various
  75         other kinds of sharing (itimers, POSIX timers, etc.).
  76
  77      CLONE_SETTLS
  78         The sixth parameter to CLONE determines the TLS area for the
  79         new thread.
  80
  81      CLONE_PARENT_SETTID
  82         The kernels writes the thread ID of the newly created thread
  83         into the location pointed to by the fifth parameters to CLONE.
  84
  85         Note that it would be semantically equivalent to use
  86         CLONE_CHILD_SETTID but it is be more expensive in the kernel.
  87
  88      CLONE_CHILD_CLEARTID
  89         The kernels clears the thread ID of a thread that has called
  90         sys_exit() in the location pointed to by the seventh parameter
  91         to CLONE.
  92
  93      The termination signal is chosen to be zero which means no signal
  94      is sent.  */
  95   const int clone_flags = (CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SYSVSEM
  96                            | CLONE_SIGHAND | CLONE_THREAD
  97                            | CLONE_SETTLS | CLONE_PARENT_SETTID
  98                            | CLONE_CHILD_CLEARTID
  99                            | 0);
 100
 101   TLS_DEFINE_INIT_TP (tp, pd);
 102
 103   if (__glibc_unlikely (ARCH_CLONE (&start_thread, STACK_VARIABLES_ARGS,
 104                                     clone_flags, pd, &pd->tid, tp, &pd->tid)
 105                         == -1))
 106     return errno;
 107
 108   /* It's started now, so if we fail below, we'll have to cancel it
 109      and let it clean itself up.  */
 110   *thread_ran = true;
 111
 112   /* Now we have the possibility to set scheduling parameters etc.  */
 113   if (attr != NULL)
 114     {
 115       int res;
 116
 117       /* Set the affinity mask if necessary.  */
 118       if (need_setaffinity)
 119         {
 120           assert (*stopped_start);
 121
 122           res = INTERNAL_SYSCALL_CALL (sched_setaffinity, pd->tid,
 123                                        attr->extension->cpusetsize,
 124                                        attr->extension->cpuset);
 125
 126           if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (res)))
 127           err_out:
 128             {
 129               /* The operation failed.  We have to kill the thread.
 130                  We let the normal cancellation mechanism do the work.  */
 131
 132               pid_t pid = __getpid ();
 133               INTERNAL_SYSCALL_CALL (tgkill, pid, pd->tid, SIGCANCEL);
 134
 135               return INTERNAL_SYSCALL_ERRNO (res);
 136             }
 137         }
 138
 139       /* Set the scheduling parameters.  */
 140       if ((attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0)
 141         {
 142           assert (*stopped_start);
 143
 144           res = INTERNAL_SYSCALL_CALL (sched_setscheduler, pd->tid,
 145                                        pd->schedpolicy, &pd->schedparam);
 146
 147           if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (res)))
 148             goto err_out;
 149         }
 150     }
 151
 152   return 0;
 153 }