sysdeps/unix/sysv/linux/nscd_setup_thread.c

   1 /* Setup of nscd worker threads.  Linux verison.
   2    Copyright (C) 2004, 2005 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@redhat.com>, 2004.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published
   8    by the Free Software Foundation; version 2 of the License, or
   9    (at your option) any later version.
  10
  11    This program 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
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software Foundation,
  18    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  19
  20 #include <string.h>
  21 #include <unistd.h>
  22 #include <nscd.h>
  23 #include <sysdep.h>
  24
  25
  26 int
  27 setup_thread (struct database_dyn *db)
  28 {
  29 #ifdef __NR_set_tid_address
  30   /* Only supported when NPTL is used.  */
  31   char buf[100];
  32   if (confstr (_CS_GNU_LIBPTHREAD_VERSION, buf, sizeof (buf)) >= sizeof (buf)
  33       || strncmp (buf, "NPTL", 4) != 0)
  34     return 0;
  35
  36   /* Do not try this at home, kids.  We play with the SETTID address
  37      even thought the process is multi-threaded.  This can only work
  38      since none of the threads ever terminates.  */
  39   INTERNAL_SYSCALL_DECL (err);
  40   int r = INTERNAL_SYSCALL (set_tid_address, err, 1,
  41                             &db->head->nscd_certainly_running);
  42   if (!INTERNAL_SYSCALL_ERROR_P (r, err))
  43     /* We know the kernel can reset this field when nscd terminates.
  44        So, set the field to a nonzero value which indicates that nscd
  45        is certainly running and clients can skip the test.  */
  46     return db->head->nscd_certainly_running = 1;
  47 #endif
  48
  49   return 0;
  50 }