hook_call_deferred() works before tasks have started

State machines implemented using deferred functions need to be able to
kick off deferred function from a HOOK_INIT handler.  But tasks aren't
running in HOOK_INIT, so task_wake() fails.

Instead, hook_call_deferred() should check to see if the hook task has
had a chance to run yet.  If it hasn't, then there's no need to wake
it; it'll get run eventually anyway.

BUG=chrome-os-partner:24892
BRANCH=rambi
TEST=Add a call to hook_call_deferred() in a HOOK_INIT handler.  It shouldn't
     crash, and the deferred function should be called.

Change-Id: I5c8077b636ae030a668a211fd8238549b6bcfa54
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/181953
Reviewed-by: Yung-chieh Lo <yjlou@chromium.org>

common/hooks.c

@@ -52,6 +52,7 @@ static const struct hook_ptrs hook_list[] = {
 /* Times for deferrable functions */
 static uint64_t defer_until[DEFERRABLE_MAX_COUNT];
 static int defer_new_call;
+static int hook_task_started;
 
 #ifdef CONFIG_HOOK_DEBUG
 /* Stats for hooks */
@@ -161,8 +162,10 @@ int hook_call_deferred(void (*routine)(void), int us)
 		 * loop one more time before sleeping.
 		 */
 		defer_new_call = 1;
+
 		/* Wake task so it can re-sleep for the proper time */
-		task_wake(TASK_ID_HOOKS);
+		if (hook_task_started)
+			task_wake(TASK_ID_HOOKS);
 	}
 
 	return EC_SUCCESS;
@@ -174,6 +177,8 @@ void hook_task(void)
 	static uint64_t last_second = -SECOND;
 	static uint64_t last_tick = -HOOK_TICK_INTERVAL;
 
+	hook_task_started = 1;
+
 	while (1) {
 		uint64_t t = get_time().val;
 		int next = 0;