168 lines
5.4 KiB
C
168 lines
5.4 KiB
C
/* Copyright (C) 2005-2022 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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#ifndef GOMP_BARRIER_H
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#define GOMP_BARRIER_H 1
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#include "mutex.h"
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typedef struct
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{
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/* Make sure total/generation is in a mostly read cacheline, while
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awaited in a separate cacheline. */
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unsigned total __attribute__((aligned (64)));
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unsigned generation;
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unsigned awaited __attribute__((aligned (64)));
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unsigned awaited_final;
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} gomp_barrier_t;
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typedef unsigned int gomp_barrier_state_t;
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/* The generation field contains a counter in the high bits, with a few
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low bits dedicated to flags. Note that TASK_PENDING and WAS_LAST can
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share space because WAS_LAST is never stored back to generation. */
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#define BAR_TASK_PENDING 1
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#define BAR_WAS_LAST 1
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#define BAR_WAITING_FOR_TASK 2
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#define BAR_CANCELLED 4
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#define BAR_INCR 8
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static inline void gomp_barrier_init (gomp_barrier_t *bar, unsigned count)
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{
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bar->total = count;
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bar->awaited = count;
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bar->awaited_final = count;
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bar->generation = 0;
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}
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static inline void gomp_barrier_reinit (gomp_barrier_t *bar, unsigned count)
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{
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__atomic_add_fetch (&bar->awaited, count - bar->total, MEMMODEL_ACQ_REL);
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bar->total = count;
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}
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static inline void gomp_barrier_destroy (gomp_barrier_t *bar)
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{
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}
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extern void gomp_barrier_wait (gomp_barrier_t *);
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extern void gomp_barrier_wait_last (gomp_barrier_t *);
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extern void gomp_barrier_wait_end (gomp_barrier_t *, gomp_barrier_state_t);
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extern void gomp_team_barrier_wait (gomp_barrier_t *);
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extern void gomp_team_barrier_wait_final (gomp_barrier_t *);
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extern void gomp_team_barrier_wait_end (gomp_barrier_t *,
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gomp_barrier_state_t);
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extern bool gomp_team_barrier_wait_cancel (gomp_barrier_t *);
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extern bool gomp_team_barrier_wait_cancel_end (gomp_barrier_t *,
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gomp_barrier_state_t);
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extern void gomp_team_barrier_wake (gomp_barrier_t *, int);
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struct gomp_team;
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extern void gomp_team_barrier_cancel (struct gomp_team *);
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static inline gomp_barrier_state_t
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gomp_barrier_wait_start (gomp_barrier_t *bar)
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{
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unsigned int ret = __atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE);
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ret &= -BAR_INCR | BAR_CANCELLED;
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/* A memory barrier is needed before exiting from the various forms
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of gomp_barrier_wait, to satisfy OpenMP API version 3.1 section
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2.8.6 flush Construct, which says there is an implicit flush during
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a barrier region. This is a convenient place to add the barrier,
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so we use MEMMODEL_ACQ_REL here rather than MEMMODEL_ACQUIRE. */
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if (__atomic_add_fetch (&bar->awaited, -1, MEMMODEL_ACQ_REL) == 0)
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ret |= BAR_WAS_LAST;
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return ret;
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}
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static inline gomp_barrier_state_t
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gomp_barrier_wait_cancel_start (gomp_barrier_t *bar)
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{
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return gomp_barrier_wait_start (bar);
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}
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/* This is like gomp_barrier_wait_start, except it decrements
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bar->awaited_final rather than bar->awaited and should be used
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for the gomp_team_end barrier only. */
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static inline gomp_barrier_state_t
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gomp_barrier_wait_final_start (gomp_barrier_t *bar)
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{
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unsigned int ret = __atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE);
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ret &= -BAR_INCR | BAR_CANCELLED;
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/* See above gomp_barrier_wait_start comment. */
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if (__atomic_add_fetch (&bar->awaited_final, -1, MEMMODEL_ACQ_REL) == 0)
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ret |= BAR_WAS_LAST;
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return ret;
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}
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static inline bool
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gomp_barrier_last_thread (gomp_barrier_state_t state)
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{
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return state & BAR_WAS_LAST;
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}
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/* All the inlines below must be called with team->task_lock
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held. */
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static inline void
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gomp_team_barrier_set_task_pending (gomp_barrier_t *bar)
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{
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bar->generation |= BAR_TASK_PENDING;
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}
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static inline void
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gomp_team_barrier_clear_task_pending (gomp_barrier_t *bar)
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{
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bar->generation &= ~BAR_TASK_PENDING;
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}
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static inline void
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gomp_team_barrier_set_waiting_for_tasks (gomp_barrier_t *bar)
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{
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bar->generation |= BAR_WAITING_FOR_TASK;
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}
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static inline bool
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gomp_team_barrier_waiting_for_tasks (gomp_barrier_t *bar)
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{
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return (bar->generation & BAR_WAITING_FOR_TASK) != 0;
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}
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static inline bool
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gomp_team_barrier_cancelled (gomp_barrier_t *bar)
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{
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return __builtin_expect ((bar->generation & BAR_CANCELLED) != 0, 0);
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}
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static inline void
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gomp_team_barrier_done (gomp_barrier_t *bar, gomp_barrier_state_t state)
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{
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bar->generation = (state & -BAR_INCR) + BAR_INCR;
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}
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#endif /* GOMP_BARRIER_H */
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