On Fri, Feb 16, 2024 at 04:59:44AM -0300, Leonardo Bras wrote:

Currently note_interrupt() will check threads_handled for changes and use
it to mark an IRQ as handled, in order to avoid having a threaded
interrupt to falsely trigger unhandled IRQ detection.

This detection can still be falsely triggered if we have many IRQ handled
accounted between each check of threads_handled, as those will be counted
as a single one in the unhandled IRQ detection.

In order to fix this, subtract from irqs_unhandled the number of IRQs
handled since the last check (threads_handled_last - threads_handled).

...

+static inline int get_handled_diff(struct irq_desc *desc)
+{
+	unsigned int handled;
+	int diff;
+
+	handled = (unsigned int)atomic_read(&desc->threads_handled);
+	handled |= SPURIOUS_DEFERRED;
+
+	diff = handled - desc->threads_handled_last;
+	diff >>= SPURIOUS_DEFERRED_SHIFT;
+
+	/*
+	 * Note: We keep the SPURIOUS_DEFERRED bit set. We are handling the
+	 * previous invocation right now. Keep it for the current one, so the
+	 * next hardware interrupt will account for it.
+	 */

+	if (diff != 0)

	if (diff)

+		desc->threads_handled_last = handled;
+
+	return diff;
+}

...

+			diff = get_handled_diff(desc);
+			if (diff > 0) {

diff may not be negative as you always right shift by 1 (or more) bit. Hence

			if (diff)

will suffice (also be aligned with the similar check inside the helper) and
making the helper to return unsigned value will be clearer. Am I correct?

-- 
With Best Regards,
Andy Shevchenko