altos: Make ao_cur_task_index track ao_cur_task in ao_yield

This keeps the two main task references (index and pointer) in
agreement during task switching, avoiding an extra assignment at the
end of the task switching loop.

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

diff --git a/src/core/ao_task.c b/src/core/ao_task.c
index 4011a36e06297f7423c85aabed8d6f2f2a0561d9..4593bd790c4717586d258489749212d5cf4a5aae 100644 (file)
--- a/src/core/ao_task.c
+++ b/src/core/ao_task.c
@@ -82,39 +82,36 @@ ao_yield(void) ao_arch_naked_define
 
        ao_arch_isr_stack();
 
-#if CHECK_STACK
+#if AO_CHECK_STACK
        in_yield = 1;
 #endif
        /* Find a task to run. If there isn't any runnable task,
         * this loop will run forever, which is just fine
         */
        {
-               __pdata uint8_t ao_next_task_index = ao_cur_task_index;
+               __pdata uint8_t ao_last_task_index = ao_cur_task_index;
                for (;;) {
-                       ++ao_next_task_index;
-                       if (ao_next_task_index == ao_num_tasks)
-                               ao_next_task_index = 0;
+                       ++ao_cur_task_index;
+                       if (ao_cur_task_index == ao_num_tasks)
+                               ao_cur_task_index = 0;
+
+                       ao_cur_task = ao_tasks[ao_cur_task_index];
 
-                       ao_cur_task = ao_tasks[ao_next_task_index];
-                       if (ao_cur_task->wchan == NULL) {
-                               ao_cur_task_index = ao_next_task_index;
+                       /* Check for ready task */
+                       if (ao_cur_task->wchan == NULL)
                                break;
-                       }
 
                        /* Check if the alarm is set for a time which has passed */
                        if (ao_cur_task->alarm &&
-                           (int16_t) (ao_time() - ao_cur_task->alarm) >= 0) {
-                               ao_cur_task_index = ao_next_task_index;
+                           (int16_t) (ao_time() - ao_cur_task->alarm) >= 0)
                                break;
-                       }
 
                        /* Enter lower power mode when there isn't anything to do */
-                       if (ao_next_task_index == ao_cur_task_index) {
+                       if (ao_cur_task_index == ao_last_task_index)
                                ao_arch_cpu_idle();
-                       }
                }
        }
-#if CHECK_STACK
+#if AO_CHECK_STACK
        cli();
        in_yield = 0;
 #endif
@@ -177,7 +174,7 @@ ao_exit(void)
 void
 ao_task_info(void)
 {
-       uint8_t i;
+       uint8_t         i;
        __xdata struct ao_task *task;
 
        for (i = 0; i < ao_num_tasks; i++) {