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- /*
- * 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 (randevouz point) implementation for N tasks.
- * Based on the Little book of sempahores - 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
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