sysdeps/unix/sysv/linux/nscd_setup_thread.c

   1 /* Setup of nscd worker threads.  Linux verison.
   2    Copyright (C) 2004-2014 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, see <http://www.gnu.org/licenses/>.  */
  18
  19 #include <string.h>
  20 #include <unistd.h>
  21 #include <nscd.h>
  22 #include <sysdep.h>
  23
  24
  25 int
  26 setup_thread (struct database_dyn *db)
  27 {
  28 #ifdef __NR_set_tid_address
  29   /* Only supported when NPTL is used.  */
  30   char buf[100];
  31   if (confstr (_CS_GNU_LIBPTHREAD_VERSION, buf, sizeof (buf)) >= sizeof (buf)
  32       || strncmp (buf, "NPTL", 4) != 0)
  33     return 0;
  34
  35   /* Do not try this at home, kids.  We play with the SETTID address
  36      even thought the process is multi-threaded.  This can only work
  37      since none of the threads ever terminates.  */
  38   INTERNAL_SYSCALL_DECL (err);
  39   int r = INTERNAL_SYSCALL (set_tid_address, err, 1,
  40                             &db->head->nscd_certainly_running);
  41   if (!INTERNAL_SYSCALL_ERROR_P (r, err))
  42     /* We know the kernel can reset this field when nscd terminates.
  43        So, set the field to a nonzero value which indicates that nscd
  44        is certainly running and clients can skip the test.  */
  45     return db->head->nscd_certainly_running = 1;
  46 #endif
  47
  48   return 0;
  49 }