1  /* Setup of nscd worker threads.  Linux version.
       2     Copyright (C) 2004-2023 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  }