nptl/sysdeps/unix/sysv/linux/sparc/sparc32/pthread_barrier_wait.c

   1 /* Copyright (C) 2003-2014 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 <errno.h>
  20 #include <sysdep.h>
  21 #include <lowlevellock.h>
  22 #include <pthreadP.h>
  23
  24 /* Wait on barrier.  */
  25 int
  26 pthread_barrier_wait (barrier)
  27      pthread_barrier_t *barrier;
  28 {
  29   union sparc_pthread_barrier *ibarrier
  30     = (union sparc_pthread_barrier *) barrier;
  31   int result = 0;
  32   int private = ibarrier->s.pshared ? LLL_SHARED : LLL_PRIVATE;
  33
  34   /* Make sure we are alone.  */
  35   lll_lock (ibarrier->b.lock, private);
  36
  37   /* One more arrival.  */
  38   --ibarrier->b.left;
  39
  40   /* Are these all?  */
  41   if (ibarrier->b.left == 0)
  42     {
  43       /* Yes. Increment the event counter to avoid invalid wake-ups and
  44          tell the current waiters that it is their turn.  */
  45       ++ibarrier->b.curr_event;
  46
  47       /* Wake up everybody.  */
  48       lll_futex_wake (&ibarrier->b.curr_event, INT_MAX, private);
  49
  50       /* This is the thread which finished the serialization.  */
  51       result = PTHREAD_BARRIER_SERIAL_THREAD;
  52     }
  53   else
  54     {
  55       /* The number of the event we are waiting for.  The barrier's event
  56          number must be bumped before we continue.  */
  57       unsigned int event = ibarrier->b.curr_event;
  58
  59       /* Before suspending, make the barrier available to others.  */
  60       lll_unlock (ibarrier->b.lock, private);
  61
  62       /* Wait for the event counter of the barrier to change.  */
  63       do
  64         lll_futex_wait (&ibarrier->b.curr_event, event, private);
  65       while (event == ibarrier->b.curr_event);
  66     }
  67
  68   /* Make sure the init_count is stored locally or in a register.  */
  69   unsigned int init_count = ibarrier->b.init_count;
  70
  71   /* If this was the last woken thread, unlock.  */
  72   if (__atomic_is_v9 || ibarrier->s.pshared == 0)
  73     {
  74       if (atomic_increment_val (&ibarrier->b.left) == init_count)
  75         /* We are done.  */
  76         lll_unlock (ibarrier->b.lock, private);
  77     }
  78   else
  79     {
  80       unsigned int left;
  81       /* Slightly more complicated.  On pre-v9 CPUs, atomic_increment_val
  82          is only atomic for threads within the same process, not for
  83          multiple processes.  */
  84       __sparc32_atomic_do_lock24 (&ibarrier->s.left_lock);
  85       left = ++ibarrier->b.left;
  86       __sparc32_atomic_do_unlock24 (&ibarrier->s.left_lock);
  87       if (left == init_count)
  88         /* We are done.  */
  89         lll_unlock (ibarrier->b.lock, private);
  90     }
  91
  92   return result;
  93 }