sysdeps/unix/sysv/linux/nscd_setup_thread.c

   1 /* Setup of nscd worker threads.  Linux version.
   2    Copyright (C) 2004-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published
   7    by the Free Software Foundation; version 2 of the License, or
   8    (at your option) any later version.
   9
  10    This program 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
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, see <https://www.gnu.org/licenses/>.  */
  17
  18 #include <string.h>
  19 #include <unistd.h>
  20 #include <nscd.h>
  21 #include <sysdep.h>
  22
  23
  24 int
  25 setup_thread (struct database_dyn *db)
  26 {
  27   /* Only supported when NPTL is used.  */
  28   char buf[100];
  29   if (confstr (_CS_GNU_LIBPTHREAD_VERSION, buf, sizeof (buf)) >= sizeof (buf)
  30       || strncmp (buf, "NPTL", 4) != 0)
  31     return 0;
  32
  33   /* Do not try this at home, kids.  We play with the SETTID address
  34      even thought the process is multi-threaded.  This can only work
  35      since none of the threads ever terminates.  */
  36   int r = INTERNAL_SYSCALL_CALL (set_tid_address,
  37                                  &db->head->nscd_certainly_running);
  38   if (!INTERNAL_SYSCALL_ERROR_P (r))
  39     /* We know the kernel can reset this field when nscd terminates.
  40        So, set the field to a nonzero value which indicates that nscd
  41        is certainly running and clients can skip the test.  */
  42     return db->head->nscd_certainly_running = 1;
  43
  44   return 0;
  45 }