fbtl/pthread_cond_signal.c

   1 /* Copyright (C) 2003-2013 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, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <endian.h>
  20 #include <errno.h>
  21 #include <sysdep.h>
  22 #include <lowlevellock.h>
  23 #include <pthread.h>
  24 #include <pthreadP.h>
  25
  26 #include <shlib-compat.h>
  27 #include <kernel-features.h>
  28 #include <stap-probe.h>
  29
  30
  31 int
  32 __pthread_cond_signal (pthread_cond_t *cond)
  33 {
  34   int pshared = (cond->__data.__mutex == (void *) ~0l)
  35                 ? LLL_SHARED : LLL_PRIVATE;
  36
  37   LIBC_PROBE (cond_signal, 1, cond);
  38
  39   /* Make sure we are alone.  */
  40   lll_lock (cond->__data.__lock, pshared);
  41
  42   /* Are there any waiters to be woken?  */
  43   if (cond->__data.__total_seq > cond->__data.__wakeup_seq)
  44     {
  45       /* Yes.  Mark one of them as woken.  */
  46       ++cond->__data.__wakeup_seq;
  47       ++cond->__data.__futex;
  48
  49 #warning TODO/rework
  50 #if 0
  51 #if (defined lll_futex_cmp_requeue_pi \
  52      && defined __ASSUME_REQUEUE_PI)
  53       int pi_flag = PTHREAD_MUTEX_PRIO_INHERIT_NP | PTHREAD_MUTEX_ROBUST_NP;
  54       pthread_mutex_t *mut = cond->__data.__mutex;
  55
  56       /* Do not use requeue for pshared condvars.  */
  57       if (mut != (void *) ~0l)
  58         pi_flag &= mut->__data.__kind;
  59
  60       if (__builtin_expect (pi_flag == PTHREAD_MUTEX_PRIO_INHERIT_NP, 0)
  61         /* This can only really fail with a ENOSYS, since nobody can modify
  62            futex while we have the cond_lock.  */
  63           && lll_futex_cmp_requeue_pi (&cond->__data.__futex, 1, 0,
  64                                        &mut->__data.__lock,
  65                                        cond->__data.__futex, pshared) == 0)
  66         {
  67           lll_unlock (cond->__data.__lock, pshared);
  68           return 0;
  69         }
  70       else
  71 #endif
  72         /* Wake one.  */
  73         if (! __builtin_expect (lll_futex_wake_unlock (&cond->__data.__futex,
  74                                                        1, 1,
  75                                                        &cond->__data.__lock,
  76                                                        pshared), 0))
  77           return 0;
  78 #endif
  79       /* Fallback if neither of them work.  */
  80       lll_futex_wake (&cond->__data.__futex, 1, pshared);
  81     }
  82
  83   /* We are done.  */
  84   lll_unlock (cond->__data.__lock, pshared);
  85
  86   return 0;
  87 }
  88
  89 versioned_symbol (libpthread, __pthread_cond_signal, pthread_cond_signal,
  90                   GLIBC_2_3_2);