From 1fdbf8d0f87d618deded242e9c22f1cebd9c7c74 Mon Sep 17 00:00:00 2001
From: Bart Van Assche <bvanassche@google.com>
Date: Fri, 17 Feb 2023 15:34:49 -0800
Subject: [PATCH] init: Combine two if-statements

Combine two if-statements. This change is fine because:
* The code between the two if-statements does not queue actions.
* If an action is queued from another thread then WakeMainInitThread()
  is called after the action has been queued.

Bug: 266255006
Change-Id: Id4b9565ff4fdb3ee2a2bbca316c8c78e0f2d38dd
Signed-off-by: Bart Van Assche <bvanassche@google.com>
---
 init/init.cpp | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)

diff --git a/init/init.cpp b/init/init.cpp
index c965fe635..05a8a9cc5 100644
--- a/init/init.cpp
+++ b/init/init.cpp
@@ -1109,8 +1109,11 @@ int SecondStageMain(int argc, char** argv) {
     // Restore prio before main loop
     setpriority(PRIO_PROCESS, 0, 0);
     while (true) {
-        // By default, sleep until something happens.
-        std::optional<std::chrono::milliseconds> epoll_timeout;
+        // By default, sleep until something happens. Do not convert far_future into
+        // std::chrono::milliseconds because that would trigger an overflow. The unit of boot_clock
+        // is 1ns.
+        const boot_clock::time_point far_future = boot_clock::time_point::max();
+        boot_clock::time_point next_action_time = far_future;
 
         auto shutdown_command = shutdown_state.CheckShutdown();
         if (shutdown_command) {
@@ -1122,23 +1125,28 @@ int SecondStageMain(int argc, char** argv) {
 
         if (!(prop_waiter_state.MightBeWaiting() || Service::is_exec_service_running())) {
             am.ExecuteOneCommand();
+            // If there's more work to do, wake up again immediately.
+            if (am.HasMoreCommands()) {
+                next_action_time = boot_clock::now();
+            }
         }
+        // Since the above code examined pending actions, no new actions must be
+        // queued by the code between this line and the Epoll::Wait() call below
+        // without calling WakeMainInitThread().
         if (!IsShuttingDown()) {
             auto next_process_action_time = HandleProcessActions();
 
             // If there's a process that needs restarting, wake up in time for that.
             if (next_process_action_time) {
-                epoll_timeout = std::chrono::ceil<std::chrono::milliseconds>(
-                        *next_process_action_time - boot_clock::now());
-                if (epoll_timeout < 0ms) epoll_timeout = 0ms;
+                next_action_time = std::min(next_action_time, *next_process_action_time);
             }
         }
 
-        if (!(prop_waiter_state.MightBeWaiting() || Service::is_exec_service_running())) {
-            // If there's more work to do, wake up again immediately.
-            if (am.HasMoreCommands()) epoll_timeout = 0ms;
+        std::optional<std::chrono::milliseconds> epoll_timeout;
+        if (next_action_time != far_future) {
+            epoll_timeout = std::chrono::ceil<std::chrono::milliseconds>(
+                    std::max(next_action_time - boot_clock::now(), 0ns));
         }
-
         auto epoll_result = epoll.Wait(epoll_timeout);
         if (!epoll_result.ok()) {
             LOG(ERROR) << epoll_result.error();