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1/*2 * Copyright 2019 Advanced Micro Devices, Inc.3 *4 * Permission is hereby granted, free of charge, to any person obtaining a5 * copy of this software and associated documentation files (the "Software"),6 * to deal in the Software without restriction, including without limitation7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,8 * and/or sell copies of the Software, and to permit persons to whom the9 * Software is furnished to do so, subject to the following conditions:10 *11 * The above copyright notice and this permission notice shall be included in12 * all copies or substantial portions of the Software.13 *14 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR15 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,16 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL17 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR18 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,19 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR20 * OTHER DEALINGS IN THE SOFTWARE.21 *22 */23#include <linux/semaphore.h>24#include <linux/atomic.h>25 26/*27 * Reusable 2 PHASE task barrier (rendez-vous point) implementation for N tasks.28 * Based on the Little book of semaphores - https://greenteapress.com/wp/semaphores/29 */30 31 32 33#ifndef DRM_TASK_BARRIER_H_34#define DRM_TASK_BARRIER_H_35 36/*37 * Represents an instance of a task barrier.38 */39struct task_barrier {40 unsigned int n;41 atomic_t count;42 struct semaphore enter_turnstile;43 struct semaphore exit_turnstile;44};45 46static inline void task_barrier_signal_turnstile(struct semaphore *turnstile,47 unsigned int n)48{49 int i;50 51 for (i = 0 ; i < n; i++)52 up(turnstile);53}54 55static inline void task_barrier_init(struct task_barrier *tb)56{57 tb->n = 0;58 atomic_set(&tb->count, 0);59 sema_init(&tb->enter_turnstile, 0);60 sema_init(&tb->exit_turnstile, 0);61}62 63static inline void task_barrier_add_task(struct task_barrier *tb)64{65 tb->n++;66}67 68static inline void task_barrier_rem_task(struct task_barrier *tb)69{70 tb->n--;71}72 73/*74 * Lines up all the threads BEFORE the critical point.75 *76 * When all thread passed this code the entry barrier is back to locked state.77 */78static inline void task_barrier_enter(struct task_barrier *tb)79{80 if (atomic_inc_return(&tb->count) == tb->n)81 task_barrier_signal_turnstile(&tb->enter_turnstile, tb->n);82 83 down(&tb->enter_turnstile);84}85 86/*87 * Lines up all the threads AFTER the critical point.88 *89 * This function is used to avoid any one thread running ahead if the barrier is90 * used repeatedly .91 */92static inline void task_barrier_exit(struct task_barrier *tb)93{94 if (atomic_dec_return(&tb->count) == 0)95 task_barrier_signal_turnstile(&tb->exit_turnstile, tb->n);96 97 down(&tb->exit_turnstile);98}99 100/* Convinieince function when nothing to be done in between entry and exit */101static inline void task_barrier_full(struct task_barrier *tb)102{103 task_barrier_enter(tb);104 task_barrier_exit(tb);105}106 107#endif108