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+/* Copyright (C) 2005, 2008, 2009 Free Software Foundation, Inc.
+ Contributed by Richard Henderson <rth@redhat.com>.
+
+ This file is part of the GNU OpenMP Library (libgomp).
+
+ Libgomp is free software; you can redistribute it and/or modify it
+ under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3, or (at your option)
+ any later version.
+
+ Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
+ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ more details.
+
+ Under Section 7 of GPL version 3, you are granted additional
+ permissions described in the GCC Runtime Library Exception, version
+ 3.1, as published by the Free Software Foundation.
+
+ You should have received a copy of the GNU General Public License and
+ a copy of the GCC Runtime Library Exception along with this program;
+ see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
+ <http://www.gnu.org/licenses/>. */
+
+/* This is a Linux specific implementation of a barrier synchronization
+ mechanism for libgomp. This type is private to the library. This
+ implementation uses atomic instructions and the futex syscall. */
+
+#include <limits.h>
+#include "wait.h"
+
+
+void
+gomp_barrier_wait_end (gomp_barrier_t *bar, gomp_barrier_state_t state)
+{
+ if (__builtin_expect ((state & 1) != 0, 0))
+ {
+ /* Next time we'll be awaiting TOTAL threads again. */
+ bar->awaited = bar->total;
+ atomic_write_barrier ();
+ bar->generation += 4;
+ futex_wake ((int *) &bar->generation, INT_MAX);
+ }
+ else
+ {
+ unsigned int generation = state;
+
+ do
+ do_wait ((int *) &bar->generation, generation);
+ while (bar->generation == generation);
+ }
+}
+
+void
+gomp_barrier_wait (gomp_barrier_t *bar)
+{
+ gomp_barrier_wait_end (bar, gomp_barrier_wait_start (bar));
+}
+
+/* Like gomp_barrier_wait, except that if the encountering thread
+ is not the last one to hit the barrier, it returns immediately.
+ The intended usage is that a thread which intends to gomp_barrier_destroy
+ this barrier calls gomp_barrier_wait, while all other threads
+ call gomp_barrier_wait_last. When gomp_barrier_wait returns,
+ the barrier can be safely destroyed. */
+
+void
+gomp_barrier_wait_last (gomp_barrier_t *bar)
+{
+ gomp_barrier_state_t state = gomp_barrier_wait_start (bar);
+ if (state & 1)
+ gomp_barrier_wait_end (bar, state);
+}
+
+void
+gomp_team_barrier_wake (gomp_barrier_t *bar, int count)
+{
+ futex_wake ((int *) &bar->generation, count == 0 ? INT_MAX : count);
+}
+
+void
+gomp_team_barrier_wait_end (gomp_barrier_t *bar, gomp_barrier_state_t state)
+{
+ unsigned int generation;
+
+ if (__builtin_expect ((state & 1) != 0, 0))
+ {
+ /* Next time we'll be awaiting TOTAL threads again. */
+ struct gomp_thread *thr = gomp_thread ();
+ struct gomp_team *team = thr->ts.team;
+ bar->awaited = bar->total;
+ atomic_write_barrier ();
+ if (__builtin_expect (team->task_count, 0))
+ {
+ gomp_barrier_handle_tasks (state);
+ state &= ~1;
+ }
+ else
+ {
+ bar->generation = state + 3;
+ futex_wake ((int *) &bar->generation, INT_MAX);
+ return;
+ }
+ }
+
+ generation = state;
+ do
+ {
+ do_wait ((int *) &bar->generation, generation);
+ if (__builtin_expect (bar->generation & 1, 0))
+ gomp_barrier_handle_tasks (state);
+ if ((bar->generation & 2))
+ generation |= 2;
+ }
+ while (bar->generation != state + 4);
+}
+
+void
+gomp_team_barrier_wait (gomp_barrier_t *bar)
+{
+ gomp_team_barrier_wait_end (bar, gomp_barrier_wait_start (bar));
+}