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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>
148 lines
4.8 KiB
C
148 lines
4.8 KiB
C
/****************************************************************************
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* sched/hrtimer/hrtimer_start.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,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations 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 <nuttx/arch.h>
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#include <nuttx/clock.h>
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#include <errno.h>
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#include "hrtimer/hrtimer.h"
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: hrtimer_insert
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*
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* Description:
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* Insert the given high-resolution timer into the active timer RB-tree.
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* If the timer is already in the tree, it will be replaced.
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* If the inserted timer becomes the earliest timer in the tree, the
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* hardware timer will be configured to fire at its expiration.
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*
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* Input Parameters:
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* hrtimer - Pointer to the hrtimer structure to be inserted.
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*
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* Returned Value:
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* OK (0) on success; negated errno value on failure.
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*
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* Assumptions/Notes:
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* - This function should be called with interrupts disabled or under
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* spinlock protection to ensure RB-tree integrity.
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* - If the timer is currently running, insertion is rejected with -EBUSY.
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****************************************************************************/
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static inline int hrtimer_insert(FAR hrtimer_t *hrtimer)
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{
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DEBUGASSERT(hrtimer != NULL);
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/* Insert (or replace) the timer into the RB-tree ordered by expiration */
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RB_INSERT(hrtimer_tree_s, &g_hrtimer_tree, &hrtimer->node);
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/* Mark the timer as armed */
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hrtimer->state = HRTIMER_STATE_ARMED;
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/* If the inserted timer is now the earliest, start hardware timer */
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if (&hrtimer->node == RB_MIN(hrtimer_tree_s, &g_hrtimer_tree))
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{
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return hrtimer_starttimer(hrtimer->expired);
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}
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return OK;
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}
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: hrtimer_start
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*
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* Description:
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* Start a high-resolution timer to expire after a specified duration
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* in nanoseconds, either as an absolute or relative time.
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*
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* Input Parameters:
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* hrtimer - Pointer to the hrtimer structure.
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* ns - Expiration time in nanoseconds. Interpretation
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* depends on mode.
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* mode - Timer mode (HRTIMER_MODE_ABS or HRTIMER_MODE_REL).
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*
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* Returned Value:
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* OK (0) on success, or a negated errno value on failure.
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*
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* Assumptions/Notes:
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* - This function disables interrupts briefly via spinlock to safely
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* insert the timer into the RB-tree.
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* - Absolute mode sets the timer to expire at the given absolute time.
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* - Relative mode sets the timer to expire after 'ns'
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* nanoseconds from the current time.
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****************************************************************************/
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int hrtimer_start(FAR hrtimer_t *hrtimer,
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uint64_t ns,
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enum hrtimer_mode_e mode)
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{
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irqstate_t flags;
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int ret = OK;
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DEBUGASSERT(hrtimer != NULL);
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/* Protect RB-tree manipulation with spinlock and disable interrupts */
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flags = spin_lock_irqsave(&g_hrtimer_spinlock);
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/* Reject start if the timer is already running or armed */
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if ((hrtimer->state == HRTIMER_STATE_RUNNING) ||
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(hrtimer->state == HRTIMER_STATE_ARMED))
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{
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spin_unlock_irqrestore(&g_hrtimer_spinlock, flags);
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return -EBUSY;
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}
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/* Compute absolute expiration time */
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if (mode == HRTIMER_MODE_ABS)
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{
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hrtimer->expired = ns;
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}
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else
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{
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hrtimer->expired = hrtimer_gettime() + ns;
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}
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/* Insert the timer into the RB-tree */
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ret = hrtimer_insert(hrtimer);
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spin_unlock_irqrestore(&g_hrtimer_spinlock, flags);
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return ret;
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}
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