nptl/pthread_cond_signal.c

   1 /* Copyright (C) 2003, 2004, 2007 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library 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 GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <endian.h>
  21 #include <errno.h>
  22 #include <sysdep.h>
  23 #include <lowlevellock.h>
  24 #include <pthread.h>
  25 #include <pthreadP.h>
  26
  27 #include <shlib-compat.h>
  28 #include <kernel-features.h>
  29
  30
  31 int
  32 __pthread_cond_signal (cond)
  33      pthread_cond_t *cond;
  34 {
  35   int pshared = (cond->__data.__mutex == (void *) ~0l)
  36                 ? LLL_SHARED : LLL_PRIVATE;
  37
  38   /* Make sure we are alone.  */
  39   lll_lock (cond->__data.__lock, pshared);
  40
  41   /* Are there any waiters to be woken?  */
  42   if (cond->__data.__total_seq > cond->__data.__wakeup_seq)
  43     {
  44       /* Yes.  Mark one of them as woken.  */
  45       ++cond->__data.__wakeup_seq;
  46       ++cond->__data.__futex;
  47
  48       /* Wake one.  */
  49       if (! __builtin_expect (lll_futex_wake_unlock (&cond->__data.__futex, 1,
  50                                                      1, &cond->__data.__lock,
  51                                                      pshared), 0))
  52         return 0;
  53
  54       lll_futex_wake (&cond->__data.__futex, 1, pshared);
  55     }
  56
  57   /* We are done.  */
  58   lll_unlock (cond->__data.__lock, pshared);
  59
  60   return 0;
  61 }
  62
  63 versioned_symbol (libpthread, __pthread_cond_signal, pthread_cond_signal,
  64                   GLIBC_2_3_2);