ueventd: make parallel restorecon functionality optional

5aa6197d5f 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/README.ueventd.md

@@ -110,3 +110,9 @@ ueventd to create the nodes.
 
 For boot time purposes, this is done in parallel across a set of child processes. `ueventd.cpp` in
 this directory contains documentation on how the parallelization is done.
+
+There is an option to parallelize the restorecon function during cold boot as well. This should only
+be done for devices that do not use genfscon, which is the recommended method for labeling sysfs
+nodes. To enable this option, use the below line in a ueventd.rc script:
+
+    parallel_restorecon enabled

init/ueventd.cpp

@@ -113,10 +113,12 @@ namespace init {
 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 @@ class ColdBoot {
     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 @@ void ColdBoot::RestoreConHandler(unsigned int process_num, unsigned int total_pr
 
         selinux_android_restorecon(dir.c_str(), SELINUX_ANDROID_RESTORECON_RECURSE);
     }
-    _exit(EXIT_SUCCESS);
 }
 
 void ColdBoot::GenerateRestoreCon(const std::string& directory) {
@@ -195,7 +198,10 @@ void ColdBoot::ForkSubProcesses() {
 
         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 @@ void ColdBoot::Run() {
 
     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 @@ int ueventd_main(int argc, char** argv) {
     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();
     }
 

init/ueventd_parser.cpp

@@ -88,18 +88,17 @@ Result<void> ParseFirmwareDirectoriesLine(std::vector<std::string>&& args,
     return {};
 }
 
-Result<void> ParseModaliasHandlingLine(std::vector<std::string>&& args,
-                                       bool* enable_modalias_handling) {
+Result<void> ParseEnabledDisabledLine(std::vector<std::string>&& args, bool* feature) {
     if (args.size() != 2) {
-        return Error() << "modalias_handling lines take exactly one parameter";
+        return Error() << args[0] << " lines take exactly one parameter";
     }
 
     if (args[1] == "enabled") {
-        *enable_modalias_handling = true;
+        *feature = true;
     } else if (args[1] == "disabled") {
-        *enable_modalias_handling = false;
+        *feature = false;
     } else {
-        return Error() << "modalias_handling takes either 'enabled' or 'disabled' as a parameter";
+        return Error() << args[0] << " takes either 'enabled' or 'disabled' as a parameter";
     }
 
     return {};
@@ -213,11 +212,14 @@ UeventdConfiguration ParseConfig(const std::vector<std::string>& configs) {
                                std::bind(ParseFirmwareDirectoriesLine, _1,
                                          &ueventd_configuration.firmware_directories));
     parser.AddSingleLineParser("modalias_handling",
-                               std::bind(ParseModaliasHandlingLine, _1,
+                               std::bind(ParseEnabledDisabledLine, _1,
                                          &ueventd_configuration.enable_modalias_handling));
     parser.AddSingleLineParser("uevent_socket_rcvbuf_size",
                                std::bind(ParseUeventSocketRcvbufSizeLine, _1,
                                          &ueventd_configuration.uevent_socket_rcvbuf_size));
+    parser.AddSingleLineParser("parallel_restorecon",
+                               std::bind(ParseEnabledDisabledLine, _1,
+                                         &ueventd_configuration.enable_parallel_restorecon));
 
     for (const auto& config : configs) {
         parser.ParseConfig(config);

init/ueventd_parser.h

@@ -14,8 +14,7 @@
  * limitations under the License.
  */
 
-#ifndef _INIT_UEVENTD_PARSER_H
-#define _INIT_UEVENTD_PARSER_H
+#pragma once
 
 #include <string>
 #include <vector>
@@ -32,11 +31,10 @@ struct UeventdConfiguration {
     std::vector<std::string> firmware_directories;
     bool enable_modalias_handling = false;
     size_t uevent_socket_rcvbuf_size = 0;
+    bool enable_parallel_restorecon = false;
 };
 
 UeventdConfiguration ParseConfig(const std::vector<std::string>& configs);
 
 }  // namespace init
 }  // namespace android
-
-#endif

init/ueventd_parser_test.cpp

@@ -147,6 +147,24 @@ uevent_socket_rcvbuf_size 8M
     TestUeventdFile(ueventd_file, {{}, {}, {}, {}, false, 8 * 1024 * 1024});
 }
 
+TEST(ueventd_parser, EnabledDisabledLines) {
+    auto ueventd_file = R"(
+modalias_handling enabled
+parallel_restorecon enabled
+modalias_handling disabled
+)";
+
+    TestUeventdFile(ueventd_file, {{}, {}, {}, {}, false, 0, true});
+
+    auto ueventd_file2 = R"(
+parallel_restorecon enabled
+modalias_handling enabled
+parallel_restorecon disabled
+)";
+
+    TestUeventdFile(ueventd_file2, {{}, {}, {}, {}, true, 0, false});
+}
+
 TEST(ueventd_parser, AllTogether) {
     auto ueventd_file = R"(
 
@@ -179,6 +197,8 @@ subsystem test_devpath_dirname
 firmware_directories /more
 
 uevent_socket_rcvbuf_size 6M
+modalias_handling enabled
+parallel_restorecon enabled
 
 #ending comment
 )";
@@ -211,7 +231,7 @@ uevent_socket_rcvbuf_size 6M
     size_t uevent_socket_rcvbuf_size = 6 * 1024 * 1024;
 
     TestUeventdFile(ueventd_file, {subsystems, sysfs_permissions, permissions, firmware_directories,
-                                   false, uevent_socket_rcvbuf_size});
+                                   true, uevent_socket_rcvbuf_size, true});
 }
 
 // All of these lines are ill-formed, so test that there is 0 output.
@@ -230,6 +250,13 @@ uevent_socket_rcvbuf_size blah
 
 subsystem #no name
 
+modalias_handling
+modalias_handling enabled enabled
+modalias_handling blah
+
+parallel_restorecon
+parallel_restorecon enabled enabled
+parallel_restorecon blah
 )";
 
     TestUeventdFile(ueventd_file, {});