mirror of https://gitee.com/openkylin/linux.git
108 lines
2.9 KiB
C
108 lines
2.9 KiB
C
/*
|
|
* 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
|