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[AMD Official Use Only - Internal Distribution Only] -----Original Message----- It is used to synchronize N threads at a rendevouz point before execution of critical code that has to be started by all the threads at approximatly the same time. Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@xxxxxxx> --- include/drm/task_barrier.h | 106 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 106 insertions(+) create mode 100644 include/drm/task_barrier.h diff --git a/include/drm/task_barrier.h b/include/drm/task_barrier.h new file mode 100644 index 0000000..81fb0f7 --- /dev/null +++ b/include/drm/task_barrier.h @@ -0,0 +1,106 @@ +/* + * 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_ + [Le]: It might be better to prefix “drm_” to the functions and structure below, even this header file name.
+/* + * Represents an instance of a task barrier. + */ +struct task_barrier { + unsigned int n; [Le]: We can define it as signed type here for more common use. + 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 of the
+reset if [Le]: No need to mention “reset” here. With the above addressed, Acked-by: Le Ma
Le.Ma@xxxxxxx Regards, Ma Le + * the barrier is used in a loop (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); +} + +static inline void task_barrier_full(struct task_barrier *tb) { + task_barrier_enter(tb); + task_barrier_exit(tb); +} + +#endif -- 2.7.4 |
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