sysdeps/sparc/sparc32/pthread_barrier_wait.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 <errno.h>
  20 #include <sysdep.h>
  21 #include <lowlevellock.h>
  22 #include <pthreadP.h>
  23 #include <sparc-nptl.h>
  24 #include <futex-internal.h>
  25
  26 /* Wait on barrier.  */
  27 int
  28 __pthread_barrier_wait (barrier)
  29      pthread_barrier_t *barrier;
  30 {
  31   union sparc_pthread_barrier *ibarrier
  32     = (union sparc_pthread_barrier *) barrier;
  33   int result = 0;
  34   int private = ibarrier->s.pshared ? LLL_SHARED : LLL_PRIVATE;
  35   int futex_private = ibarrier->s.pshared ? FUTEX_SHARED : FUTEX_PRIVATE;
  36
  37   /* Make sure we are alone.  */
  38   lll_lock (ibarrier->b.lock, private);
  39
  40   /* One more arrival.  */
  41   --ibarrier->b.left;
  42
  43   /* Are these all?  */
  44   if (ibarrier->b.left == 0)
  45     {
  46       /* Yes. Increment the event counter to avoid invalid wake-ups and
  47          tell the current waiters that it is their turn.  */
  48       ++ibarrier->b.curr_event;
  49
  50       /* Wake up everybody.  */
  51       futex_wake (&ibarrier->b.curr_event, INT_MAX, futex_private);
  52
  53       /* This is the thread which finished the serialization.  */
  54       result = PTHREAD_BARRIER_SERIAL_THREAD;
  55     }
  56   else
  57     {
  58       /* The number of the event we are waiting for.  The barrier's event
  59          number must be bumped before we continue.  */
  60       unsigned int event = ibarrier->b.curr_event;
  61
  62       /* Before suspending, make the barrier available to others.  */
  63       lll_unlock (ibarrier->b.lock, private);
  64
  65       /* Wait for the event counter of the barrier to change.  */
  66       do
  67         futex_wait_simple (&ibarrier->b.curr_event, event, futex_private);
  68       while (event == ibarrier->b.curr_event);
  69     }
  70
  71   /* Make sure the init_count is stored locally or in a register.  */
  72   unsigned int init_count = ibarrier->b.init_count;
  73
  74   /* If this was the last woken thread, unlock.  */
  75   if (__atomic_is_v9 || ibarrier->s.pshared == 0)
  76     {
  77       if (atomic_increment_val (&ibarrier->b.left) == init_count)
  78         /* We are done.  */
  79         lll_unlock (ibarrier->b.lock, private);
  80     }
  81   else
  82     {
  83       unsigned int left;
  84       /* Slightly more complicated.  On pre-v9 CPUs, atomic_increment_val
  85          is only atomic for threads within the same process, not for
  86          multiple processes.  */
  87       __sparc32_atomic_do_lock24 (&ibarrier->s.left_lock);
  88       left = ++ibarrier->b.left;
  89       __sparc32_atomic_do_unlock24 (&ibarrier->s.left_lock);
  90       if (left == init_count)
  91         /* We are done.  */
  92         lll_unlock (ibarrier->b.lock, private);
  93     }
  94
  95   return result;
  96 }
  97 weak_alias (__pthread_barrier_wait, pthread_barrier_wait)