init: Prevent spin loop while waiting for exec or property
Currently, when we are waiting for an exec service or a property, if
there are either any services to be restarted or any more commands to
be run, we set the epoll_timeout to handle these events. However, we
don't actually restart and processes or execute any commands while
waiting, so this essentially turns this waiting into a spin loop,
particularly in the common case of having more commands to execute,
where epoll_timeout is set to 0.
The change only sets epoll_timeout if we're not waiting.
Note that the only way to stop waiting for an exec service or a
property is for a signal or property to be delivered to init, which
happens through the epoll fds, so it's safe to indefinitely wait for
epoll to return.
Test: Boot bullhead
Change-Id: Iae3b217eb28182038b464fd39df8e7d27b5e23ff
diff --git a/init/init.cpp b/init/init.cpp
index 0ce1c05..23448d6 100644
--- a/init/init.cpp
+++ b/init/init.cpp
@@ -1322,22 +1322,24 @@
am.QueueBuiltinAction(queue_property_triggers_action, "queue_property_triggers");
while (true) {
- if (!(waiting_for_exec || waiting_for_prop)) {
- am.ExecuteOneCommand();
- restart_processes();
- }
-
// By default, sleep until something happens.
int epoll_timeout_ms = -1;
- // If there's a process that needs restarting, wake up in time for that.
- if (process_needs_restart_at != 0) {
- epoll_timeout_ms = (process_needs_restart_at - time(nullptr)) * 1000;
- if (epoll_timeout_ms < 0) epoll_timeout_ms = 0;
+ if (!(waiting_for_exec || waiting_for_prop)) {
+ am.ExecuteOneCommand();
}
+ if (!(waiting_for_exec || waiting_for_prop)) {
+ restart_processes();
- // If there's more work to do, wake up again immediately.
- if (am.HasMoreCommands()) epoll_timeout_ms = 0;
+ // If there's a process that needs restarting, wake up in time for that.
+ if (process_needs_restart_at != 0) {
+ epoll_timeout_ms = (process_needs_restart_at - time(nullptr)) * 1000;
+ if (epoll_timeout_ms < 0) epoll_timeout_ms = 0;
+ }
+
+ // If there's more work to do, wake up again immediately.
+ if (am.HasMoreCommands()) epoll_timeout_ms = 0;
+ }
epoll_event ev;
int nr = TEMP_FAILURE_RETRY(epoll_wait(epoll_fd, &ev, 1, epoll_timeout_ms));