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author | Andrey Grodzovsky <andrey.grodzovsky@amd.com> | 2019-12-06 12:26:33 -0500 |
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committer | Alex Deucher <alexander.deucher@amd.com> | 2019-12-18 16:09:12 -0500 |
commit | 368fd0aad1bec2bb30a3e5e905b2aedd8d15feb7 (patch) | |
tree | 64cf72b9875f0385a46aeea5efc490c581f9d8a0 /include/drm | |
parent | 041a62bc0603544c97ac407df67bd60398ce0668 (diff) | |
download | linux-368fd0aad1bec2bb30a3e5e905b2aedd8d15feb7.tar.gz linux-368fd0aad1bec2bb30a3e5e905b2aedd8d15feb7.tar.bz2 linux-368fd0aad1bec2bb30a3e5e905b2aedd8d15feb7.zip |
drm: Add Reusable task barrier.
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.
v2: Remove mention of reset use case, improve doc.
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: Le Ma <Le.Ma@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Diffstat (limited to 'include/drm')
-rw-r--r-- | include/drm/task_barrier.h | 107 |
1 files changed, 107 insertions, 0 deletions
diff --git a/include/drm/task_barrier.h b/include/drm/task_barrier.h new file mode 100644 index 000000000000..087e3f649c52 --- /dev/null +++ b/include/drm/task_barrier.h @@ -0,0 +1,107 @@ +/* + * 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 |