/* * Copyright 2019 Advanced Micro Devices, Inc. * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the "Software"), * to deal in the Software without restriction, including without limitation * the rights to use, copy, modify, merge, publish, distribute, sublicense, * and/or sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR * OTHER DEALINGS IN THE SOFTWARE. * */#include <linux/semaphore.h>#include <linux/atomic.h> /* * Reusable 2 PHASE task barrier (rendez-vous point) implementation for N tasks. * Based on the Little book of semaphores - https://greenteapress.com/wp/semaphores/ */   #ifndef DRM_TASK_BARRIER_H_#define DRM_TASK_BARRIER_H_ /* * Represents an instance of a task barrier. */struct task_barrier {	unsigned int n;	atomic_t count;	struct semaphore enter_turnstile;	struct semaphore exit_turnstile;}; static inline void task_barrier_signal_turnstile(struct semaphore *turnstile,						 unsigned int n){	int i; 	for (i = 0 ; i < n; i++)		up(turnstile);} static inline void task_barrier_init(struct task_barrier *tb){	tb->n = 0;	atomic_set(&tb->count, 0);	sema_init(&tb->enter_turnstile, 0);	sema_init(&tb->exit_turnstile, 0);} static inline void task_barrier_add_task(struct task_barrier *tb){	tb->n++;} static inline void task_barrier_rem_task(struct task_barrier *tb){	tb->n--;} /* * Lines up all the threads BEFORE the critical point. * * When all thread passed this code the entry barrier is back to locked state. */static inline void task_barrier_enter(struct task_barrier *tb){	if (atomic_inc_return(&tb->count) == tb->n)		task_barrier_signal_turnstile(&tb->enter_turnstile, tb->n); 	down(&tb->enter_turnstile);} /* * Lines up all the threads AFTER the critical point. * * This function is used to avoid any one thread running ahead if the barrier is *  used repeatedly . */static inline void task_barrier_exit(struct task_barrier *tb){	if (atomic_dec_return(&tb->count) == 0)		task_barrier_signal_turnstile(&tb->exit_turnstile, tb->n); 	down(&tb->exit_turnstile);} /* Convinieince function when nothing to be done in between entry and exit */static inline void task_barrier_full(struct task_barrier *tb){	task_barrier_enter(tb);	task_barrier_exit(tb);} #endif