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

   1 /* Copyright (C) 2003, 2004, 2006 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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <errno.h>
  21 #include <sysdep.h>
  22 #include <lowlevellock.h>
  23 #include <pthreadP.h>
  24
  25 struct sparc_pthread_barrier
  26 {
  27   struct pthread_barrier b;
  28   unsigned char left_lock;
  29   unsigned char pshared;
  30 };
  31
  32 /* Wait on barrier.  */
  33 int
  34 pthread_barrier_wait (barrier)
  35      pthread_barrier_t *barrier;
  36 {
  37   struct sparc_pthread_barrier *ibarrier
  38     = (struct sparc_pthread_barrier *) barrier;
  39   int result = 0;
  40
  41   /* Make sure we are alone.  */
  42   lll_lock (ibarrier->b.lock);
  43
  44   /* One more arrival.  */
  45   --ibarrier->b.left;
  46
  47   /* Are these all?  */
  48   if (ibarrier->b.left == 0)
  49     {
  50       /* Yes. Increment the event counter to avoid invalid wake-ups and
  51          tell the current waiters that it is their turn.  */
  52       ++ibarrier->b.curr_event;
  53
  54       /* Wake up everybody.  */
  55       lll_futex_wake (&ibarrier->b.curr_event, INT_MAX);
  56
  57       /* This is the thread which finished the serialization.  */
  58       result = PTHREAD_BARRIER_SERIAL_THREAD;
  59     }
  60   else
  61     {
  62       /* The number of the event we are waiting for.  The barrier's event
  63          number must be bumped before we continue.  */
  64       unsigned int event = ibarrier->b.curr_event;
  65
  66       /* Before suspending, make the barrier available to others.  */
  67       lll_unlock (ibarrier->b.lock);
  68
  69       /* Wait for the event counter of the barrier to change.  */
  70       do
  71         lll_futex_wait (&ibarrier->b.curr_event, event);
  72       while (event == ibarrier->b.curr_event);
  73     }
  74
  75   /* Make sure the init_count is stored locally or in a register.  */
  76   unsigned int init_count = ibarrier->b.init_count;
  77
  78   /* If this was the last woken thread, unlock.  */
  79   if (__atomic_is_v9 || ibarrier->pshared == 0)
  80     {
  81       if (atomic_increment_val (&ibarrier->b.left) == init_count)
  82         /* We are done.  */
  83         lll_unlock (ibarrier->b.lock);
  84     }
  85   else
  86     {
  87       unsigned int left;
  88       /* Slightly more complicated.  On pre-v9 CPUs, atomic_increment_val
  89          is only atomic for threads within the same process, not for
  90          multiple processes.  */
  91       __sparc32_atomic_do_lock24 (&ibarrier->left_lock);
  92       left = ++ibarrier->b.left;
  93       __sparc32_atomic_do_unlock24 (&ibarrier->left_lock);
  94       if (left == init_count)
  95         /* We are done.  */
  96         lll_unlock (ibarrier->b.lock);
  97     }
  98
  99   return result;
 100 }