| /* Copyright (C) 2015-2022 Free Software Foundation, Inc. |
| Contributed by Mentor Embedded. |
| |
| This file is part of the GNU Offloading and Multi Processing 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 an AMD GCN specific implementation of a barrier synchronization |
| mechanism for libgomp. This type is private to the library. This |
| implementation uses atomic instructions and s_barrier instruction. It |
| uses MEMMODEL_RELAXED here because barriers are within workgroups and |
| therefore don't need to flush caches. */ |
| |
| #include <limits.h> |
| #include "libgomp.h" |
| |
| |
| void |
| gomp_barrier_wait_end (gomp_barrier_t *bar, gomp_barrier_state_t state) |
| { |
| if (__builtin_expect (state & BAR_WAS_LAST, 0)) |
| { |
| /* Next time we'll be awaiting TOTAL threads again. */ |
| bar->awaited = bar->total; |
| __atomic_store_n (&bar->generation, bar->generation + BAR_INCR, |
| MEMMODEL_RELAXED); |
| } |
| if (bar->total > 1) |
| asm ("s_barrier" ::: "memory"); |
| } |
| |
| 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) |
| { |
| /* Deferring to gomp_barrier_wait does not use the optimization opportunity |
| allowed by the interface contract for all-but-last participants. The |
| original implementation in config/linux/bar.c handles this better. */ |
| gomp_barrier_wait (bar); |
| } |
| |
| void |
| gomp_team_barrier_wake (gomp_barrier_t *bar, int count) |
| { |
| if (bar->total > 1) |
| asm ("s_barrier" ::: "memory"); |
| } |
| |
| void |
| gomp_team_barrier_wait_end (gomp_barrier_t *bar, gomp_barrier_state_t state) |
| { |
| unsigned int generation, gen; |
| |
| if (__builtin_expect (state & BAR_WAS_LAST, 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; |
| team->work_share_cancelled = 0; |
| if (__builtin_expect (team->task_count, 0)) |
| { |
| gomp_barrier_handle_tasks (state); |
| state &= ~BAR_WAS_LAST; |
| } |
| else |
| { |
| state &= ~BAR_CANCELLED; |
| state += BAR_INCR - BAR_WAS_LAST; |
| __atomic_store_n (&bar->generation, state, MEMMODEL_RELAXED); |
| if (bar->total > 1) |
| asm ("s_barrier" ::: "memory"); |
| return; |
| } |
| } |
| |
| generation = state; |
| state &= ~BAR_CANCELLED; |
| int retry = 100; |
| do |
| { |
| if (retry-- == 0) |
| { |
| /* It really shouldn't happen that barriers get out of sync, but |
| if they do then this will loop until they realign, so we need |
| to avoid an infinite loop where the thread just isn't there. */ |
| const char msg[] = ("Barrier sync failed (another thread died?);" |
| " aborting."); |
| write (2, msg, sizeof (msg)-1); |
| abort(); |
| } |
| |
| asm ("s_barrier" ::: "memory"); |
| gen = __atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE); |
| if (__builtin_expect (gen & BAR_TASK_PENDING, 0)) |
| { |
| gomp_barrier_handle_tasks (state); |
| gen = __atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE); |
| } |
| generation |= gen & BAR_WAITING_FOR_TASK; |
| } |
| while (gen != state + BAR_INCR); |
| } |
| |
| void |
| gomp_team_barrier_wait (gomp_barrier_t *bar) |
| { |
| gomp_team_barrier_wait_end (bar, gomp_barrier_wait_start (bar)); |
| } |
| |
| void |
| gomp_team_barrier_wait_final (gomp_barrier_t *bar) |
| { |
| gomp_barrier_state_t state = gomp_barrier_wait_final_start (bar); |
| if (__builtin_expect (state & BAR_WAS_LAST, 0)) |
| bar->awaited_final = bar->total; |
| gomp_team_barrier_wait_end (bar, state); |
| } |
| |
| bool |
| gomp_team_barrier_wait_cancel_end (gomp_barrier_t *bar, |
| gomp_barrier_state_t state) |
| { |
| unsigned int generation, gen; |
| |
| if (__builtin_expect (state & BAR_WAS_LAST, 0)) |
| { |
| /* Next time we'll be awaiting TOTAL threads again. */ |
| /* BAR_CANCELLED should never be set in state here, because |
| cancellation means that at least one of the threads has been |
| cancelled, thus on a cancellable barrier we should never see |
| all threads to arrive. */ |
| struct gomp_thread *thr = gomp_thread (); |
| struct gomp_team *team = thr->ts.team; |
| |
| bar->awaited = bar->total; |
| team->work_share_cancelled = 0; |
| if (__builtin_expect (team->task_count, 0)) |
| { |
| gomp_barrier_handle_tasks (state); |
| state &= ~BAR_WAS_LAST; |
| } |
| else |
| { |
| state += BAR_INCR - BAR_WAS_LAST; |
| __atomic_store_n (&bar->generation, state, MEMMODEL_RELAXED); |
| if (bar->total > 1) |
| asm ("s_barrier" ::: "memory"); |
| return false; |
| } |
| } |
| |
| if (__builtin_expect (state & BAR_CANCELLED, 0)) |
| return true; |
| |
| generation = state; |
| int retry = 100; |
| do |
| { |
| if (retry-- == 0) |
| { |
| /* It really shouldn't happen that barriers get out of sync, but |
| if they do then this will loop until they realign, so we need |
| to avoid an infinite loop where the thread just isn't there. */ |
| const char msg[] = ("Barrier sync failed (another thread died?);" |
| " aborting."); |
| write (2, msg, sizeof (msg)-1); |
| abort(); |
| } |
| |
| if (bar->total > 1) |
| asm ("s_barrier" ::: "memory"); |
| gen = __atomic_load_n (&bar->generation, MEMMODEL_RELAXED); |
| if (__builtin_expect (gen & BAR_CANCELLED, 0)) |
| return true; |
| if (__builtin_expect (gen & BAR_TASK_PENDING, 0)) |
| { |
| gomp_barrier_handle_tasks (state); |
| gen = __atomic_load_n (&bar->generation, MEMMODEL_RELAXED); |
| } |
| generation |= gen & BAR_WAITING_FOR_TASK; |
| } |
| while (gen != state + BAR_INCR); |
| |
| return false; |
| } |
| |
| bool |
| gomp_team_barrier_wait_cancel (gomp_barrier_t *bar) |
| { |
| return gomp_team_barrier_wait_cancel_end (bar, gomp_barrier_wait_start (bar)); |
| } |
| |
| void |
| gomp_team_barrier_cancel (struct gomp_team *team) |
| { |
| gomp_mutex_lock (&team->task_lock); |
| if (team->barrier.generation & BAR_CANCELLED) |
| { |
| gomp_mutex_unlock (&team->task_lock); |
| return; |
| } |
| team->barrier.generation |= BAR_CANCELLED; |
| gomp_mutex_unlock (&team->task_lock); |
| gomp_team_barrier_wake (&team->barrier, INT_MAX); |
| } |