Fix-Point commented on code in PR #17573:
URL: https://github.com/apache/nuttx/pull/17573#discussion_r2659514058
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sched/hrtimer/hrtimer_process.c:
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@@ -94,32 +106,36 @@ void hrtimer_process(uint64_t now)
RB_REMOVE(hrtimer_tree_s, &g_hrtimer_tree, &hrtimer->node);
- /* Ensure the timer callback is valid */
+ /* Increment running reference counter */
+
+ hrtimer->cpus++;
- DEBUGASSERT(hrtimer->func != NULL);
+ /* cpus is a running reference counter and must never wrap */
- hrtimer->state = HRTIMER_STATE_RUNNING;
+ DEBUGASSERT(hrtimer->cpus != 0);
- spin_unlock_irqrestore(&g_hrtimer_spinlock, flags);
+ /* Leave critical section before invoking the callback */
+
+ write_sequnlock_irqrestore(&g_hrtimer_spinlock, flags);
/* Invoke the timer callback */
- period = hrtimer->func(hrtimer);
+ period = func(arg);
- flags = spin_lock_irqsave(&g_hrtimer_spinlock);
+ /* Re-enter critical section to update timer state */
- if ((hrtimer->state == HRTIMER_STATE_CANCELED) || (period == 0))
- {
- /* Timer is canceled or one-shot; mark it inactive */
+ flags = write_seqlock_irqsave(&g_hrtimer_spinlock);
- hrtimer->state = HRTIMER_STATE_INACTIVE;
- }
- else
+ hrtimer->cpus--;
+
+ /* Re-arm periodic timer if not canceled or re-armed concurrently */
+
+ if (period > 0 && hrtimer->expired == expired)
Review Comment:
I still stand by what I stated before:
> Designing correct concurrent algorithms requires systematic consideration.
As I stated in #17570, after carefully reviewing your implementation, I could
not really find a good solution that preserves version information without
introducing significant performance or memory-overhead overhead.
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