static void evtchn_2l_handle_events()

in events/events_2l.c [164:262]

• 57 lines of code
• 12 McCabe index (conditional complexity)

static void evtchn_2l_handle_events(unsigned cpu, struct evtchn_loop_ctrl *ctrl)
{
	int irq;
	xen_ulong_t pending_words;
	xen_ulong_t pending_bits;
	int start_word_idx, start_bit_idx;
	int word_idx, bit_idx;
	int i;
	struct shared_info *s = HYPERVISOR_shared_info;
	struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);

	/* Timer interrupt has highest priority. */
	irq = irq_from_virq(cpu, VIRQ_TIMER);
	if (irq != -1) {
		evtchn_port_t evtchn = evtchn_from_irq(irq);
		word_idx = evtchn / BITS_PER_LONG;
		bit_idx = evtchn % BITS_PER_LONG;
		if (active_evtchns(cpu, s, word_idx) & (1ULL << bit_idx))
			generic_handle_irq(irq);
	}

	/*
	 * Master flag must be cleared /before/ clearing
	 * selector flag. xchg_xen_ulong must contain an
	 * appropriate barrier.
	 */
	pending_words = xchg_xen_ulong(&vcpu_info->evtchn_pending_sel, 0);

	start_word_idx = __this_cpu_read(current_word_idx);
	start_bit_idx = __this_cpu_read(current_bit_idx);

	word_idx = start_word_idx;

	for (i = 0; pending_words != 0; i++) {
		xen_ulong_t words;

		words = MASK_LSBS(pending_words, word_idx);

		/*
		 * If we masked out all events, wrap to beginning.
		 */
		if (words == 0) {
			word_idx = 0;
			bit_idx = 0;
			continue;
		}
		word_idx = EVTCHN_FIRST_BIT(words);

		pending_bits = active_evtchns(cpu, s, word_idx);
		bit_idx = 0; /* usually scan entire word from start */
		/*
		 * We scan the starting word in two parts.
		 *
		 * 1st time: start in the middle, scanning the
		 * upper bits.
		 *
		 * 2nd time: scan the whole word (not just the
		 * parts skipped in the first pass) -- if an
		 * event in the previously scanned bits is
		 * pending again it would just be scanned on
		 * the next loop anyway.
		 */
		if (word_idx == start_word_idx) {
			if (i == 0)
				bit_idx = start_bit_idx;
		}

		do {
			xen_ulong_t bits;
			evtchn_port_t port;

			bits = MASK_LSBS(pending_bits, bit_idx);

			/* If we masked out all events, move on. */
			if (bits == 0)
				break;

			bit_idx = EVTCHN_FIRST_BIT(bits);

			/* Process port. */
			port = (word_idx * BITS_PER_EVTCHN_WORD) + bit_idx;
			handle_irq_for_port(port, ctrl);

			bit_idx = (bit_idx + 1) % BITS_PER_EVTCHN_WORD;

			/* Next caller starts at last processed + 1 */
			__this_cpu_write(current_word_idx,
					 bit_idx ? word_idx :
					 (word_idx+1) % BITS_PER_EVTCHN_WORD);
			__this_cpu_write(current_bit_idx, bit_idx);
		} while (bit_idx != 0);

		/* Scan start_l1i twice; all others once. */
		if ((word_idx != start_word_idx) || (i != 0))
			pending_words &= ~(1UL << word_idx);

		word_idx = (word_idx + 1) % BITS_PER_EVTCHN_WORD;
	}
}