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54adf5979c
In the current NuttX kernel implementation, there is no function
to represent pure scheduler ticks.
The existing clock_systime_ticks() cannot serve this purpose,
because it keeps increasing even when the scheduler is not running.
This happens since the returned value reflects real hardware time:
as long as the timer or alarm hardware is active,
clock_systime_ticks() will continuously increase.
This patch introduces two new functions that provide access to
scheduler ticks — a counter that only increases when the scheduler
itself is running.
Signed-off-by: Chengdong Wang wangchengdong@lixiang.com
112 lines
3.5 KiB
C
112 lines
3.5 KiB
C
/****************************************************************************
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* sched/clock/clock_sched_ticks.c
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <stdint.h>
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#include <nuttx/irq.h>
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#include <nuttx/arch.h>
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#include <nuttx/clock.h>
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#include "clock/clock.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: clock_increase_sched_ticks
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*
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* Description:
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* Increment the scheduler tick counter. This function should be called
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* each time the real-time clock interrupt occurs, indicating the passage
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* of one or more scheduling ticks.
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*
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* Input Parameters:
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* ticks - The number of ticks to increment (typically 1)
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*
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* Returned Value:
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* None
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*
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****************************************************************************/
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void clock_increase_sched_ticks(clock_t ticks)
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{
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/* Increment the per-tick scheduler counter */
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#ifdef CONFIG_SYSTEM_TIME64
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atomic64_fetch_add((FAR atomic64_t *)&g_system_ticks, ticks);
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#else
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atomic_fetch_add((FAR atomic_t *)&g_system_ticks, ticks);
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#endif
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}
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/****************************************************************************
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* Name: clock_get_sched_ticks
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*
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* Description:
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* Return the current value of the scheduler tick counter. This counter
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* only increases while the scheduler is running, and is independent of
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* the real-time clock.
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*
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* Returned Value:
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* The current number of scheduler ticks.
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*
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****************************************************************************/
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clock_t clock_get_sched_ticks(void)
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{
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#ifdef CONFIG_SYSTEM_TIME64
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clock_t sample;
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clock_t verify;
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/* 64-bit accesses are not atomic on most architectures. The following
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* loop samples the 64-bit counter twice and retries in the rare case
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* that a 32-bit rollover occurs between samples.
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*
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* If no 32-bit rollover occurs:
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* - The MS 32 bits of both samples will be identical, and
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* - The LS 32 bits of the second sample will be greater than or equal
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* to those of the first.
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*/
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do
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{
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verify = g_system_ticks;
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sample = g_system_ticks;
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}
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while ((sample & TIMER_MASK32) < (verify & TIMER_MASK32) ||
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(sample & ~TIMER_MASK32) != (verify & ~TIMER_MASK32));
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return sample;
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#else
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/* On 32-bit systems, atomic access is guaranteed */
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return g_system_ticks;
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#endif
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}
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