212 lines
6.1 KiB
C
212 lines
6.1 KiB
C
/* Copyright (C) 2005-2019 Free Software Foundation, Inc.
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Contributed by Richard Henderson <rth@redhat.com>.
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This file is part of the GNU Offloading and Multi Processing Library
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(libgomp).
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Libgomp is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3, or (at your option)
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any later version.
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Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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more details.
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Under Section 7 of GPL version 3, you are granted additional
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permissions described in the GCC Runtime Library Exception, version
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3.1, as published by the Free Software Foundation.
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You should have received a copy of the GNU General Public License and
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a copy of the GCC Runtime Library Exception along with this program;
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see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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<http://www.gnu.org/licenses/>. */
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/* This is a Linux specific implementation of a barrier synchronization
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mechanism for libgomp. This type is private to the library. This
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implementation uses atomic instructions and the futex syscall. */
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#include <limits.h>
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#include "wait.h"
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void
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gomp_barrier_wait_end (gomp_barrier_t *bar, gomp_barrier_state_t state)
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{
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if (__builtin_expect (state & BAR_WAS_LAST, 0))
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{
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/* Next time we'll be awaiting TOTAL threads again. */
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bar->awaited = bar->total;
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__atomic_store_n (&bar->generation, bar->generation + BAR_INCR,
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MEMMODEL_RELEASE);
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futex_wake ((int *) &bar->generation, INT_MAX);
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}
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else
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{
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do
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do_wait ((int *) &bar->generation, state);
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while (__atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE) == state);
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}
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}
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void
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gomp_barrier_wait (gomp_barrier_t *bar)
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{
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gomp_barrier_wait_end (bar, gomp_barrier_wait_start (bar));
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}
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/* Like gomp_barrier_wait, except that if the encountering thread
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is not the last one to hit the barrier, it returns immediately.
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The intended usage is that a thread which intends to gomp_barrier_destroy
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this barrier calls gomp_barrier_wait, while all other threads
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call gomp_barrier_wait_last. When gomp_barrier_wait returns,
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the barrier can be safely destroyed. */
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void
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gomp_barrier_wait_last (gomp_barrier_t *bar)
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{
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gomp_barrier_state_t state = gomp_barrier_wait_start (bar);
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if (state & BAR_WAS_LAST)
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gomp_barrier_wait_end (bar, state);
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}
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void
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gomp_team_barrier_wake (gomp_barrier_t *bar, int count)
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{
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futex_wake ((int *) &bar->generation, count == 0 ? INT_MAX : count);
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}
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void
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gomp_team_barrier_wait_end (gomp_barrier_t *bar, gomp_barrier_state_t state)
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{
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unsigned int generation, gen;
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if (__builtin_expect (state & BAR_WAS_LAST, 0))
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{
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/* Next time we'll be awaiting TOTAL threads again. */
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struct gomp_thread *thr = gomp_thread ();
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struct gomp_team *team = thr->ts.team;
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bar->awaited = bar->total;
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team->work_share_cancelled = 0;
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if (__builtin_expect (team->task_count, 0))
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{
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gomp_barrier_handle_tasks (state);
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state &= ~BAR_WAS_LAST;
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}
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else
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{
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state &= ~BAR_CANCELLED;
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state += BAR_INCR - BAR_WAS_LAST;
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__atomic_store_n (&bar->generation, state, MEMMODEL_RELEASE);
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futex_wake ((int *) &bar->generation, INT_MAX);
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return;
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}
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}
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generation = state;
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state &= ~BAR_CANCELLED;
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do
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{
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do_wait ((int *) &bar->generation, generation);
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gen = __atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE);
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if (__builtin_expect (gen & BAR_TASK_PENDING, 0))
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{
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gomp_barrier_handle_tasks (state);
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gen = __atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE);
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}
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generation |= gen & BAR_WAITING_FOR_TASK;
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}
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while (gen != state + BAR_INCR);
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}
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void
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gomp_team_barrier_wait (gomp_barrier_t *bar)
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{
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gomp_team_barrier_wait_end (bar, gomp_barrier_wait_start (bar));
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}
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void
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gomp_team_barrier_wait_final (gomp_barrier_t *bar)
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{
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gomp_barrier_state_t state = gomp_barrier_wait_final_start (bar);
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if (__builtin_expect (state & BAR_WAS_LAST, 0))
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bar->awaited_final = bar->total;
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gomp_team_barrier_wait_end (bar, state);
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}
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bool
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gomp_team_barrier_wait_cancel_end (gomp_barrier_t *bar,
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gomp_barrier_state_t state)
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{
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unsigned int generation, gen;
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if (__builtin_expect (state & BAR_WAS_LAST, 0))
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{
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/* Next time we'll be awaiting TOTAL threads again. */
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/* BAR_CANCELLED should never be set in state here, because
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cancellation means that at least one of the threads has been
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cancelled, thus on a cancellable barrier we should never see
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all threads to arrive. */
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struct gomp_thread *thr = gomp_thread ();
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struct gomp_team *team = thr->ts.team;
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bar->awaited = bar->total;
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team->work_share_cancelled = 0;
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if (__builtin_expect (team->task_count, 0))
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{
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gomp_barrier_handle_tasks (state);
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state &= ~BAR_WAS_LAST;
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}
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else
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{
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state += BAR_INCR - BAR_WAS_LAST;
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__atomic_store_n (&bar->generation, state, MEMMODEL_RELEASE);
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futex_wake ((int *) &bar->generation, INT_MAX);
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return false;
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}
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}
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if (__builtin_expect (state & BAR_CANCELLED, 0))
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return true;
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generation = state;
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do
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{
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do_wait ((int *) &bar->generation, generation);
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gen = __atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE);
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if (__builtin_expect (gen & BAR_CANCELLED, 0))
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return true;
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if (__builtin_expect (gen & BAR_TASK_PENDING, 0))
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{
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gomp_barrier_handle_tasks (state);
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gen = __atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE);
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}
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generation |= gen & BAR_WAITING_FOR_TASK;
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}
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while (gen != state + BAR_INCR);
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return false;
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}
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bool
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gomp_team_barrier_wait_cancel (gomp_barrier_t *bar)
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{
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return gomp_team_barrier_wait_cancel_end (bar, gomp_barrier_wait_start (bar));
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}
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void
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gomp_team_barrier_cancel (struct gomp_team *team)
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{
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gomp_mutex_lock (&team->task_lock);
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if (team->barrier.generation & BAR_CANCELLED)
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{
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gomp_mutex_unlock (&team->task_lock);
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return;
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}
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team->barrier.generation |= BAR_CANCELLED;
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gomp_mutex_unlock (&team->task_lock);
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futex_wake ((int *) &team->barrier.generation, INT_MAX);
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}
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