commit 4233ec7f66d54d30109c838d09b358f21e214011
author Tom Cherry <tomcherry@google.com> Fri Sep 06 10:52:31 2019 -0700
committer Tom Cherry <tomcherry@google.com> Mon Sep 09 09:02:48 2019 -0700
tree c72d0322a78fdc005a600bb3ead293067f8b356d
parent 50e408db2d1bd015f87996f98b0bc21a39402ab0

ueventd: make parallel restorecon functionality optional

5aa6197d5f387579ff04c330001840d6988e825f added the ability to
parallelize restorecon to speed up boot for devices that have not
completely moved to genfscon.  This parallel restorecon happens after
the parallel ueventd handling.

This causes a performance regression for devices that have moved to
genfscon, since previously, the restorecon() was done in the main
ueventd thread in parallel with the uevent handlers.

I also tried to run the fully parallelized restorecon in parallel with
the uevent handlers, but that did not make any change to the cold boot
time, likely due to the additional overhead of parallelizing the work.

Bug: 140458170
Test: blueline coldboot time returns to pre-regression time.
Change-Id: I3cd6a869cc9b62792466813d94ad6c69834e854e

init/ueventd.cpp

diff --git a/init/ueventd.cpp b/init/ueventd.cpp
index cffc1b9..6741e2a 100644
--- a/init/ueventd.cpp
+++ b/init/ueventd.cpp
@@ -113,10 +113,12 @@
 class ColdBoot {
   public:
     ColdBoot(UeventListener& uevent_listener,
-             std::vector<std::unique_ptr<UeventHandler>>& uevent_handlers)
+             std::vector<std::unique_ptr<UeventHandler>>& uevent_handlers,
+             bool enable_parallel_restorecon)
         : uevent_listener_(uevent_listener),
           uevent_handlers_(uevent_handlers),
-          num_handler_subprocesses_(std::thread::hardware_concurrency() ?: 4) {}
+          num_handler_subprocesses_(std::thread::hardware_concurrency() ?: 4),
+          enable_parallel_restorecon_(enable_parallel_restorecon) {}
 
     void Run();
 
@@ -132,6 +134,8 @@
     std::vector<std::unique_ptr<UeventHandler>>& uevent_handlers_;
 
     unsigned int num_handler_subprocesses_;
+    bool enable_parallel_restorecon_;
+
     std::vector<Uevent> uevent_queue_;
 
     std::set<pid_t> subprocess_pids_;
@@ -155,7 +159,6 @@
 
         selinux_android_restorecon(dir.c_str(), SELINUX_ANDROID_RESTORECON_RECURSE);
     }
-    _exit(EXIT_SUCCESS);
 }
 
 void ColdBoot::GenerateRestoreCon(const std::string& directory) {
@@ -195,7 +198,10 @@
 
         if (pid == 0) {
             UeventHandlerMain(i, num_handler_subprocesses_);
-            RestoreConHandler(i, num_handler_subprocesses_);
+            if (enable_parallel_restorecon_) {
+                RestoreConHandler(i, num_handler_subprocesses_);
+            }
+            _exit(EXIT_SUCCESS);
         }
 
         subprocess_pids_.emplace(pid);
@@ -240,14 +246,20 @@
 
     RegenerateUevents();
 
-    selinux_android_restorecon("/sys", 0);
-    selinux_android_restorecon("/sys/devices", 0);
-    GenerateRestoreCon("/sys");
-    // takes long time for /sys/devices, parallelize it
-    GenerateRestoreCon("/sys/devices");
+    if (enable_parallel_restorecon_) {
+        selinux_android_restorecon("/sys", 0);
+        selinux_android_restorecon("/sys/devices", 0);
+        GenerateRestoreCon("/sys");
+        // takes long time for /sys/devices, parallelize it
+        GenerateRestoreCon("/sys/devices");
+    }
 
     ForkSubProcesses();
 
+    if (!enable_parallel_restorecon_) {
+        selinux_android_restorecon("/sys", SELINUX_ANDROID_RESTORECON_RECURSE);
+    }
+
     WaitForSubProcesses();
 
     android::base::SetProperty(kColdBootDoneProp, "true");
@@ -293,7 +305,8 @@
     UeventListener uevent_listener(ueventd_configuration.uevent_socket_rcvbuf_size);
 
     if (!android::base::GetBoolProperty(kColdBootDoneProp, false)) {
-        ColdBoot cold_boot(uevent_listener, uevent_handlers);
+        ColdBoot cold_boot(uevent_listener, uevent_handlers,
+                           ueventd_configuration.enable_parallel_restorecon);
         cold_boot.Run();
     }