static void power_pmu_read(struct perf_event *event)
{
	s64 val, delta, prev;

	if (event->hw.state & PERF_HES_STOPPED)
		return;

	if (!event->hw.idx)
		return;
	/*
	 * Performance monitor interrupts come even when interrupts
	 * are soft-disabled, as long as interrupts are hard-enabled.
	 * Therefore we treat them like NMIs.
	 */
	do {
		prev = local64_read(&event->hw.prev_count);
		barrier();
		val = read_pmc(event->hw.idx);
	} while (local64_cmpxchg(&event->hw.prev_count, prev, val) != prev);

	/* The counters are only 32 bits wide */
	delta = (val - prev) & 0xfffffffful;
	local64_add(delta, &event->count);
	local64_sub(delta, &event->hw.period_left);
}

This weakness involves numeric computation errors, such as integer overflows, underflows, or precision losses, which can lead to miscalculations and exploitable behaviors in software.