nptl/pthread_cond_broadcast.c

   1 /* Copyright (C) 2003, 2004, 2006, 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, 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       /* Do not use requeue for pshared condvars.  */
  57       if (cond->__data.__mutex == (void *) ~0l)
  58         goto wake_all;
  59
  60       /* Wake everybody.  */
  61       pthread_mutex_t *mut = (pthread_mutex_t *) cond->__data.__mutex;
  62
  63       /* XXX: Kernel so far doesn't support requeue to PI futex.  */
  64       /* XXX: Kernel so far can only requeue to the same type of futex,
  65          in this case private (we don't requeue for pshared condvars).  */
  66       if (__builtin_expect (mut->__data.__kind
  67                             & (PTHREAD_MUTEX_PRIO_INHERIT_NP
  68                                | PTHREAD_MUTEX_PSHARED_BIT), 0))
  69         goto wake_all;
  70
  71       /* lll_futex_requeue returns 0 for success and non-zero
  72          for errors.  */
  73       if (__builtin_expect (lll_futex_requeue (&cond->__data.__futex, 1,
  74                                                INT_MAX, &mut->__data.__lock,
  75                                                futex_val, LLL_PRIVATE), 0))
  76         {
  77           /* The requeue functionality is not available.  */
  78         wake_all:
  79           lll_futex_wake (&cond->__data.__futex, INT_MAX, pshared);
  80         }
  81
  82       /* That's all.  */
  83       return 0;
  84     }
  85
  86   /* We are done.  */
  87   lll_unlock (cond->__data.__lock, pshared);
  88
  89   return 0;
  90 }
  91
  92 versioned_symbol (libpthread, __pthread_cond_broadcast, pthread_cond_broadcast,
  93                   GLIBC_2_3_2);