nuttx/sched/hrtimer/hrtimer.h

/****************************************************************************
 * sched/hrtimer/hrtimer.h
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ****************************************************************************/

#ifndef __SCHED_HRTIMER_HRTIMER_H
#define __SCHED_HRTIMER_HRTIMER_H

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>
#include <nuttx/arch.h>
#include <nuttx/clock.h>
#include <nuttx/hrtimer.h>
#include <nuttx/seqlock.h>

#include "sched/sched.h"

#ifdef CONFIG_HRTIMER

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/* Delay used while waiting for a running hrtimer callback to complete */

#define HRTIMER_CANCEL_SYNC_DELAY_US CONFIG_USEC_PER_TICK

/****************************************************************************
 * Public Types
 ****************************************************************************/

/* Red-black tree head for managing active high-resolution timers.
 *
 * Timers are ordered by expiration time, the earliest expiring timer
 * being the left-most (minimum) node in the tree.
 */

#ifdef CONFIG_HRTIMER_TREE
RB_HEAD(hrtimer_tree_s, hrtimer_node_s);
#endif

/****************************************************************************
 * Public Data
 ****************************************************************************/

/* Seqcount protecting access to the hrtimer queue and timer state */

extern seqcount_t g_hrtimer_lock;

#ifdef CONFIG_HRTIMER_TREE
/* Red-Black tree containing all active high-resolution timers */

extern struct hrtimer_tree_s g_hrtimer_tree;
#else
/* List containing all active high-resolution timers */

extern struct list_node g_hrtimer_list;
#endif

/* Array of pointers to currently running high-resolution timers
 * for each CPU in SMP configurations. Index corresponds to CPU ID.
 */

#ifdef CONFIG_SMP
extern uintptr_t g_hrtimer_running[CONFIG_SMP_NCPUS];
#endif

/****************************************************************************
 * Public Function Prototypes
 ****************************************************************************/

/****************************************************************************
 * Name: hrtimer_process
 *
 * Description:
 *   Called from the timer interrupt handler to process expired
 *   high-resolution timers. If a timer has expired, its callback
 *   function will be executed in the context of the timer interrupt.
 *
 * Input Parameters:
 *   now - The current time (nsecs).
 *
 * Returned Value:
 *   None
 ****************************************************************************/

void hrtimer_process(uint64_t now);

/****************************************************************************
 * Inline Functions
 ****************************************************************************/

/****************************************************************************
 * Name: hrtimer_reprogram
 *
 * Description:
 *   Reprogram the hardware timer to expire at a specified nanosecond time.
 *   Converts the nanosecond time to timespec and calls the platform-specific
 *   timer start function.
 *
 * Input Parameters:
 *   ns - Expiration time in nanoseconds.
 *
 * Returned Value:
 *   OK (0) on success, negated errno on failure.
 ****************************************************************************/

static inline_function void hrtimer_reprogram(uint64_t next_expired)
{
#ifdef CONFIG_SCHED_TICKLESS
  int ret;
  struct timespec ts;
#  ifdef CONFIG_SCHED_TICKLESS_ALARM
  clock_nsec2time(&ts, next_expired);
  ret = up_alarm_start(&ts);
#  else
  struct timespec current;
  up_timer_gettime(&current);
  clock_nsec2time(&ts, next_expired);
  clock_timespec_subtract(&ts, &current, &ts);
  ret = up_timer_start(&ts);
#  endif
  DEBUGASSERT(ret == 0);
#endif
}

/****************************************************************************
 * Name: hrtimer_compare
 *
 * Description:
 *   Compare two high-resolution timer nodes to determine their ordering
 *   in the container. Used internally by the RB-tree macros.
 *
 * Input Parameters:
 *   a - Pointer to the first hrtimer node.
 *   b - Pointer to the second hrtimer node.
 *
 * Returned Value:
 *   <0 if a expires before b
 *   >=0 if a expires after b
 ****************************************************************************/

#ifdef CONFIG_HRTIMER_TREE
static inline_function
int hrtimer_compare(FAR const hrtimer_node_t *a,
                    FAR const hrtimer_node_t *b)
{
  FAR const hrtimer_t *atimer = (FAR const hrtimer_t *)a;
  FAR const hrtimer_t *btimer = (FAR const hrtimer_t *)b;

  return clock_compare(atimer->expired, btimer->expired) ? -1 : 1;
}
#endif

/****************************************************************************
 * Red-Black Tree Prototype for high-resolution timers
 *
 * Description:
 *   Declare the RB-tree prototype that manages all active high-resolution
 *   timers. This tree provides efficient insertion, removal, and lookup
 *   operations based on timer expiration time.
 ****************************************************************************/

#ifdef CONFIG_HRTIMER_TREE
RB_PROTOTYPE(hrtimer_tree_s, hrtimer_node_s, entry, hrtimer_compare);
#endif

/****************************************************************************
 * Name: hrtimer_is_armed
 *
 * Description:
 *   Test whether a timer is currently armed (inserted into the container).
 *
 * Returned Value:
 *   true if armed, false otherwise.
 ****************************************************************************/

static inline_function bool hrtimer_is_armed(FAR hrtimer_t *hrtimer)
{
  return hrtimer->func != NULL;
}

/****************************************************************************
 * Name: hrtimer_remove
 *
 * Description:
 *   Remove a timer from the container and mark it as unarmed.
 ****************************************************************************/

static inline_function void hrtimer_remove(FAR hrtimer_t *hrtimer)
{
#ifdef CONFIG_HRTIMER_TREE
  RB_REMOVE(hrtimer_tree_s, &g_hrtimer_tree, &hrtimer->node);
#else
  list_delete_fast(&hrtimer->node.entry);
#endif

  /* Explicitly mark the timer as unarmed */

  hrtimer->func = NULL;
}

/****************************************************************************
 * Name: hrtimer_insert
 *
 * Description:
 *   Insert a timer into the timer container according to its
 *   expiration time.
 ****************************************************************************/

static inline_function void hrtimer_insert(FAR hrtimer_t *hrtimer)
{
#ifdef CONFIG_HRTIMER_TREE
  RB_INSERT(hrtimer_tree_s, &g_hrtimer_tree, &hrtimer->node);
#else
  FAR hrtimer_t *curr;
  uint64_t expired = hrtimer->expired;

  list_for_every_entry(&g_hrtimer_list, curr, hrtimer_t, node.entry)
    {
      /* Until curr->expired has not timed out relative to expired */

      if (!clock_compare(curr->expired, expired))
        {
          break;
        }
    }

  list_add_before(&curr->node.entry, &hrtimer->node.entry);
#endif
}

/****************************************************************************
 * Name: hrtimer_get_first
 *
 * Description:
 *   Return the earliest expiring armed timer.
 *
 * Returned Value:
 *   Pointer to the earliest timer, or NULL if none are armed.
 ****************************************************************************/

static inline_function FAR hrtimer_t *hrtimer_get_first(void)
{
#ifdef CONFIG_HRTIMER_TREE
  return (FAR hrtimer_t *)RB_MIN(hrtimer_tree_s, &g_hrtimer_tree);
#else
  return list_first_entry(&g_hrtimer_list, FAR hrtimer_t, node.entry);
#endif
}

/****************************************************************************
 * Name: hrtimer_is_first
 *
 * Description:
 *   Test whether the given high-resolution timer is the earliest
 *   expiring timer in the container.
 *
 *   In a container ordered by expiration time, the earliest timer
 *   is represented by the left-most node. Therefore, a timer is the
 *   earliest one if it has no left child.
 *
 * Input Parameters:
 *   hrtimer - Pointer to the high-resolution timer to be tested.
 *
 * Returned Value:
 *   true  - The timer is the earliest expiring armed timer.
 *   false - The timer is not the earliest timer.
 ****************************************************************************/

static inline_function bool hrtimer_is_first(FAR hrtimer_t *hrtimer)
{
#ifdef CONFIG_HRTIMER_TREE
  return RB_LEFT(&hrtimer->node, entry) == NULL;
#else
  return hrtimer == list_first_entry(&g_hrtimer_list, hrtimer_t, node.entry);
#endif
}

/****************************************************************************
 * Name: hrtimer_read_64/32
 *
 * Description:
 *   Internal function to read the value in the queue atomically.
 *   Do not use this function if you are not sure about the thread-safe
 *   of the value you are reading.
 *
 * Input Parameters:
 *   ptr   - The pointer to be read.
 *
 * Returned Value:
 *   The value in the queue.
 *
 ****************************************************************************/

#ifdef CONFIG_ARCH_64BIT
/* On 64-bit architectures, read/write uint64_t is atomic. */
#  define hrtimer_read_64(ptr) (*(FAR volatile uint64_t *)(ptr))
#else
static inline_function
uint64_t hrtimer_read_64(FAR const uint64_t *ptr)
{
  uint64_t val;
  uint32_t seq;

  do
    {
      seq = read_seqbegin(&g_hrtimer_lock);
      val = *ptr;
    }
  while (read_seqretry(&g_hrtimer_lock, seq));

  return val;
}
#endif

#if UINT_MAX >= UINT32_MAX
/* On 32/64-bit architectures, read/write uint32_t is atomic. */
#  define hrtimer_read_32(ptr) (*(FAR volatile uint32_t *)(ptr))
#else
static inline_function
uint32_t hrtimer_read_32(FAR const uint32_t *ptr)
{
  uint32_t val;
  uint32_t seq;

  do
    {
      seq = read_seqbegin(&g_hrtimer_lock);
      val = *ptr;
    }
  while (read_seqretry(&g_hrtimer_lock, seq));

  return val;
}
#endif

/* Generic function to read the value in the queue atomically. */

#define hrtimer_read(ptr) \
  (sizeof(*(ptr)) == 8u ? \
   hrtimer_read_64((FAR const uint64_t *)(ptr)) : \
   (sizeof(*(ptr)) == 4u ? \
    hrtimer_read_32((FAR const uint32_t *)(ptr)) : 0u))

/****************************************************************************
 * Name: hrtimer_mark_running
 *
 * Description:
 *   Mark the timer as running.
 *
 * Input Parameters:
 *   timer - The timer to be marked.
 *   cpu   - The CPU core Id.
 *
 * Returned Value:
 *   None.
 *
 * Assumption:
 *   The caller must hold the lock.
 *
 ****************************************************************************/

#ifdef CONFIG_SMP
#  define hrtimer_mark_running(timer, cpu) \
  (g_hrtimer_running[cpu] = (uintptr_t)(timer))
#else
#  define hrtimer_mark_running(timer, cpu) UNUSED(cpu)
#endif
#define hrtimer_unmark_running(cpu) hrtimer_mark_running(NULL, cpu)

/****************************************************************************
 * Name: hrtimer_is_running
 *
 * Description:
 *   Check if the CPU core is running the timer.
 *
 * Input Parameters:
 *   timer - The timer to be marked.
 *   cpu   - The CPU core Id.
 *
 * Returned Value:
 *   true if the CPU core is running the timer, false otherwise.
 *
 ****************************************************************************/

#ifdef CONFIG_SMP
#  define hrtimer_is_running(timer, cpu) \
  (hrtimer_read(&g_hrtimer_running[cpu]) == (uintptr_t)(timer))
#else
#  define hrtimer_is_running(timer, cpu) (true)
#endif
#define hrtimer_is_cancelling(timer, cpu) \
  hrtimer_is_running((uintptr_t)(timer) | 0x1u, cpu)

/****************************************************************************
 * Name: hrtimer_cancel_running
 *
 * Description:
 *   Cancel the timer, revoke the ownership of the cancelled timer, and
 *   return the references count to the timer.
 *
 * Input Parameters:
 *   hrtimer - The cancelled timer.
 *
 * Returned Value:
 *   The references count to the timer.
 *
 * Assumption:
 *   The caller must hold the queue lock.
 *
 ****************************************************************************/

static inline_function
int hrtimer_cancel_running(FAR hrtimer_t *timer)
{
  int refs            = 0;
#ifdef CONFIG_SMP
  uintptr_t cancelled = (uintptr_t)timer | 0x1u;
  int cpu;

  /* Check if the timer is referenced by any CPU core.
   * Generally, only one reference to a timer can exist at the same time.
   * However, when a timer may be restarted at the cancelled state,
   * more references to the timer may exist.
   */

  unroll_loop(CONFIG_SMP_NCPUS) /* Tell the compiler to unroll the loop. */

  for (cpu = 0; cpu < CONFIG_SMP_NCPUS; cpu++)
    {
      /* This is a faster implementation equivalent to
       * (g_hrtimer_running[cpu] & (~(uintptr_t)0x1u)) == timer,
       * Assuming the pointer of the timer is at least 2-bytes aligned
       * (the last bit must be zero).
       */

      if ((g_hrtimer_running[cpu] ^ cancelled) <= 0x1u)
        {
          /* Set the timer to the cancelled state and revoke the write
           * ownership of the timer from the queue.
           */

          g_hrtimer_running[cpu] = cancelled;
          refs++;
        }
    }
#endif

  return refs;
}

/****************************************************************************
 * Name: hrtimer_wait
 *
 * Description:
 *   Wait for all references to be released before the timer can be freed.
 *
 * Input Parameters:
 *   timer - The hrtimer to be waited.
 *
 * Returned Value:
 *   None.
 *
 * Assumption:
 *   The periodical hrtimer should be cancelled before calling this function.
 *
 ****************************************************************************/

#ifdef CONFIG_SMP
static inline_function void hrtimer_wait(FAR hrtimer_t *timer)
{
  int cpu;

  DEBUGASSERT(timer && timer->func == NULL);

  /* Wait until all references have been released. */

  for (cpu = 0; cpu < CONFIG_SMP_NCPUS; cpu++)
    {
      /* The timer should not be restarted again.
       * Or there will be ownership invariant violation.
       */

      DEBUGASSERT(!hrtimer_is_running(timer, cpu));

      /* If sleeping is permitted, yield the CPU briefly to avoid
       * busy-waiting.  Otherwise, spin until the callback completes
       * and the state becomes inactive.
       */

      while (hrtimer_is_cancelling(timer, cpu))
        {
          if (!up_interrupt_context() && !is_idle_task(this_task()))
            {
              nxsched_usleep(HRTIMER_CANCEL_SYNC_DELAY_US);
            }

          /* Otherwise, spin-wait is enough. */
        }
    }

  /* Finally, we acquire the ownership of this hrtimer. */
}
#else
#  define hrtimer_wait(timer) /* Nothing to wait in non-SMP. */
#endif

#endif /* CONFIG_HRTIMER */
#endif /* __SCHED_HRTIMER_HRTIMER_H */