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wangchengdong
ed1cb6f9b8
NuttX provides the wdog module to implement timers for the scheduler. While it is lightweight and efficient, wdog only supports tick-level timers, typically in milliseconds. Although the tick duration can be configured, setting it to microsecond or nanosecond resolution is not practical. Doing so may cause an interrupt storm, where the CPU is constantly occupied handling tick interrupts. To address this limitation, a new hrtimer module is introduced. It coexists with the wdog module, providing both tick-level timers for wdog and high-resolution timers (nanosecond-level) directly to users. Signed-off-by: Chengdong Wang <wangchengdong@lixiang.com>
144 lines
4.4 KiB
C
144 lines
4.4 KiB
C
/****************************************************************************
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* sched/hrtimer/hrtimer_process.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 <assert.h>
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#include <nuttx/arch.h>
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#include <nuttx/clock.h>
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#include "hrtimer/hrtimer.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: hrtimer_process
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*
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* Description:
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* Process all expired high-resolution timers. This function repeatedly
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* retrieves the earliest timer from the active timer RB-tree, checks if it
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* has expired relative to the current time, removes it from the tree,
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* and invokes its callback function. Processing continues until:
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*
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* 1. No additional timers have expired, or
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* 2. The active timer set is empty.
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*
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* After all expired timers are processed, the next expiration event is
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* scheduled based on:
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*
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* - The earliest remaining timer, or
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* - A fallback expiration (current time + HRTIMER_DEFAULT_INCREMENT)
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* if no timers remain.
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*
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* Input Parameters:
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* ts - Pointer to the current high-resolution timestamp.
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*
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* Returned Value:
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* None.
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*
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* Assumptions/Notes:
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* - This function acquires a spinlock to protect the timer RB-tree.
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* - Timer callbacks are invoked with interrupts enabled
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* to avoid deadlocks.
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* - DEBUGASSERT ensures that timer callbacks are valid.
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****************************************************************************/
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void hrtimer_process(uint64_t now)
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{
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FAR hrtimer_t *hrtimer;
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uint64_t expired;
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uint32_t period = 0;
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irqstate_t flags;
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/* Lock the hrtimer RB-tree to protect access */
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flags = spin_lock_irqsave(&g_hrtimer_spinlock);
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/* Fetch the earliest active timer */
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hrtimer = (FAR hrtimer_t *)RB_MIN(hrtimer_tree_s, &g_hrtimer_tree);
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while (hrtimer != NULL)
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{
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/* Check if the timer has expired */
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if (!clock_compare(hrtimer->expired, now))
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{
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break;
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}
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/* Remove the expired timer from the active tree */
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RB_REMOVE(hrtimer_tree_s, &g_hrtimer_tree, &hrtimer->node);
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/* Ensure the timer callback is valid */
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DEBUGASSERT(hrtimer->func != NULL);
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hrtimer->state = HRTIMER_STATE_RUNNING;
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spin_unlock_irqrestore(&g_hrtimer_spinlock, flags);
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/* Invoke the timer callback */
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period = hrtimer->func(hrtimer);
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flags = spin_lock_irqsave(&g_hrtimer_spinlock);
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if ((hrtimer->state == HRTIMER_STATE_CANCELED) || (period == 0))
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{
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/* Timer is canceled or one-shot; mark it inactive */
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hrtimer->state = HRTIMER_STATE_INACTIVE;
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}
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else
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{
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/* Restart the periodic timer */
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hrtimer->expired += period;
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hrtimer->state = HRTIMER_STATE_ARMED;
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RB_INSERT(hrtimer_tree_s, &g_hrtimer_tree, &hrtimer->node);
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}
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/* Fetch the next earliest timer */
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hrtimer = (FAR hrtimer_t *)RB_MIN(hrtimer_tree_s, &g_hrtimer_tree);
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}
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/* Schedule the next timer expiration */
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if (hrtimer != NULL)
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{
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/* Start timer for the next earliest expiration */
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(void)hrtimer_starttimer(hrtimer->expired);
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}
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/* Leave critical section */
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spin_unlock_irqrestore(&g_hrtimer_spinlock, flags);
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}
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