sysdeps/unix/sysv/linux/nscd_setup_thread.c

   1 /* Setup of nscd worker threads.  Linux verison.
   2    Copyright (C) 2004 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    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, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <string.h>
  22 #include <unistd.h>
  23 #include <nscd.h>
  24 #include <sysdep.h>
  25
  26
  27 void
  28 setup_thread (struct database_dyn *db)
  29 {
  30 #ifdef __NR_set_tid_address
  31   /* Only supported when NPTL is used.  */
  32   char buf[100];
  33   if (confstr (_CS_GNU_LIBPTHREAD_VERSION, buf, sizeof (buf)) >= sizeof (buf)
  34       || strncmp (buf, "NPTL", 4) != 0)
  35     return;
  36
  37   /* Do not try this at home, kids.  We play with the SETTID address
  38      even thought the process is multi-threaded.  This can only work
  39      since none of the threads ever terminates.  */
  40   INTERNAL_SYSCALL_DECL (err);
  41   int r = INTERNAL_SYSCALL (set_tid_address, err, 1,
  42                             &db->head->nscd_certainly_running);
  43   if (!INTERNAL_SYSCALL_ERROR_P (r, err))
  44     /* We know the kernel can reset this field when nscd terminates.
  45        So, set the field to a nonzero value which indicates that nscd
  46        is certainly running and clients can skip the test.  */
  47     db->head->nscd_certainly_running = 1;
  48 #endif
  49 }