altos: Don't wait while idle if trying to minimize interrupt latency

Keeping the scanout running reasonably means keeping interrupt latency
constant, and that requires leaving the CPU running. Don't wait for
interrupts when the system is running in this mode.

Signed-off-by: Keith Packard <keithp@keithp.com>

diff --git a/src/kernel/ao_task.c b/src/kernel/ao_task.c
index e8a092aaf660fcf6bbec48706e14d2f7936e297b..de23ea02421013e4186801b85664abb81630d99a 100644 (file)
--- a/src/kernel/ao_task.c
+++ b/src/kernel/ao_task.c
@@ -373,7 +373,11 @@ ao_yield(void) ao_arch_naked_define
                if (!ao_list_is_empty(&run_queue))
                        break;
                /* Wait for interrupts when there's nothing ready */
-               ao_arch_wait_interrupt();
+               if (ao_task_minimize_latency) {
+                       ao_arch_release_interrupts();
+                       ao_arch_block_interrupts();
+               } else
+                       ao_arch_wait_interrupt();
        }
        ao_cur_task = ao_list_first_entry(&run_queue, struct ao_task, queue);
 #else