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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));
}
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