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sched/hrtimer: Fix functional correctness issue in SMP.

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Since the hrtimer->expired is not monotonic, it can not be used as the
version. This commit added the ownership encoding to ensure the
invariant that the cancelled the timer can not modify the hrtimer again.

Signed-off-by: ouyangxiangzhen <ouyangxiangzhen@xiaomi.com>
This commit is contained in:
ouyangxiangzhen
2026-01-15 10:58:21 +08:00
committed by GUIDINGLI
parent 47ce6590b7
commit d18fd4640e
6 changed files with 185 additions and 63 deletions
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include/nuttx/hrtimer.h
+23 -16
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@@ -125,23 +125,31 @@ extern "C"
* Name: hrtimer_cancel
*
* Description:
* Cancel a high-resolution timer.
*
* If the timer is armed but has not yet expired, it will be removed from
* the timer queue and the callback will not be invoked.
*
* If the timer callback is currently executing, this function will mark
* the timer as canceled and return immediately. The running callback is
* allowed to complete, but it will not be invoked again.
* Cancel a high-resolution timer asynchronously. This function set the
* timer to the cancelled state. The caller will acquire the limited
* ownership of the hrtimer, which allow the caller restart the hrtimer,
* but the callback function may still be executing on another CPU, which
* prevent the caller from freeing the hrtimer. The caller must call
* `hrtimer_cancel` to wait for the callback to be finished. Please use
* the function with care. Concurrency errors are prone to occur in this
* use case.
*
* This function is non-blocking and does not wait for a running callback
* to finish.
*
* Input Parameters:
* hrtimer - Timer instance to cancel
* hrtimer - Pointer to the high-resolution timer instance to cancel.
*
* Returned Value:
* OK on success; a negated errno value on failure.
* OK (0) on success; a negated errno value on failure.
* > 0 on if the timer callback is running.
*
* Assumptions/Notes:
* - This function acquires the global hrtimer spinlock to protect both
* the red-black tree and the timer state.
* - The caller must ensure that the timer structure is not freed until
* it is guaranteed that any running callback has returned.
*
****************************************************************************/
int hrtimer_cancel(FAR hrtimer_t *hrtimer);
@@ -152,12 +160,11 @@ int hrtimer_cancel(FAR hrtimer_t *hrtimer);
* Description:
* Cancel a high-resolution timer and wait until it becomes inactive.
*
* - Calls hrtimer_cancel() to request timer cancellation.
* - If the timer callback is running, waits until it completes and
* the timer state transitions to HRTIMER_STATE_INACTIVE.
* - If sleeping is allowed (normal task context), yields CPU briefly
* to avoid busy-waiting.
* - Otherwise (interrupt or idle task context), spins until completion.
* Cancel a high-resolution timer and synchronously wait the callback to
* be finished. This function set the timer to the cancelled state and wait
* for all references to be released. The caller will then acquire full
* ownership of the hrtimer. After the function returns, the caller can
* safely deallocate the hrtimer.
*
* Input Parameters:
* hrtimer - Pointer to the high-resolution timer instance to cancel.