nptl/pthread_cond_broadcast.c

   1 /* Copyright (C) 2003-2015 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 #include <stap-probe.h>
  26
  27 #include <shlib-compat.h>
  28 #include <kernel-features.h>
  29
  30
  31 int
  32 __pthread_cond_broadcast (cond)
  33      pthread_cond_t *cond;
  34 {
  35   LIBC_PROBE (cond_broadcast, 1, cond);
  36
  37   int pshared = (cond->__data.__mutex == (void *) ~0l)
  38                 ? LLL_SHARED : LLL_PRIVATE;
  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 them all as woken.  */
  46       cond->__data.__wakeup_seq = cond->__data.__total_seq;
  47       cond->__data.__woken_seq = cond->__data.__total_seq;
  48       cond->__data.__futex = (unsigned int) cond->__data.__total_seq * 2;
  49       int futex_val = cond->__data.__futex;
  50       /* Signal that a broadcast happened.  */
  51       ++cond->__data.__broadcast_seq;
  52
  53       /* We are done.  */
  54       lll_unlock (cond->__data.__lock, pshared);
  55
  56       /* Wake everybody.  */
  57       pthread_mutex_t *mut = (pthread_mutex_t *) cond->__data.__mutex;
  58
  59       /* Do not use requeue for pshared condvars.  */
  60       if (mut == (void *) ~0l
  61           || PTHREAD_MUTEX_PSHARED (mut) & PTHREAD_MUTEX_PSHARED_BIT)
  62         goto wake_all;
  63
  64 #if (defined lll_futex_cmp_requeue_pi \
  65      && defined __ASSUME_REQUEUE_PI)
  66       if (USE_REQUEUE_PI (mut))
  67         {
  68           if (lll_futex_cmp_requeue_pi (&cond->__data.__futex, 1, INT_MAX,
  69                                         &mut->__data.__lock, futex_val,
  70                                         LLL_PRIVATE) == 0)
  71             return 0;
  72         }
  73       else
  74 #endif
  75         /* lll_futex_requeue returns 0 for success and non-zero
  76            for errors.  */
  77         if (!__builtin_expect (lll_futex_requeue (&cond->__data.__futex, 1,
  78                                                   INT_MAX, &mut->__data.__lock,
  79                                                   futex_val, LLL_PRIVATE), 0))
  80           return 0;
  81
  82 wake_all:
  83       lll_futex_wake (&cond->__data.__futex, INT_MAX, pshared);
  84       return 0;
  85     }
  86
  87   /* We are done.  */
  88   lll_unlock (cond->__data.__lock, pshared);
  89
  90   return 0;
  91 }
  92
  93 versioned_symbol (libpthread, __pthread_cond_broadcast, pthread_cond_broadcast,
  94                   GLIBC_2_3_2);