Load kernel modules in parallel

First, we load independent module in parallel, then we singly load
modules which have soft-dependencies. then remove them from dependency
list of other modules. Repeat these steps until all modules are loaded.

Bug: 180676019
Test: boot successfully, and save more than 400 ms on Pixel 6 Pro.
Signed-off-by: chungkai <chungkai@google.com>
Change-Id: Ib844cfee72d4049bd951528692c818b4fa6c8e8f

init/first_stage_init.cpp

@@ -123,7 +123,7 @@ std::string GetModuleLoadList(bool recovery, const std::string& dir_path) {
 }
 
 #define MODULE_BASE_DIR "/lib/modules"
-bool LoadKernelModules(bool recovery, bool want_console, int& modules_loaded) {
+bool LoadKernelModules(bool recovery, bool want_console, bool want_parallel, int& modules_loaded) {
     struct utsname uts;
     if (uname(&uts)) {
         LOG(FATAL) << "Failed to get kernel version.";
@@ -172,7 +172,8 @@ bool LoadKernelModules(bool recovery, bool want_console, int& modules_loaded) {
     }
 
     Modprobe m({MODULE_BASE_DIR}, GetModuleLoadList(recovery, MODULE_BASE_DIR));
-    bool retval = m.LoadListedModules(!want_console);
+    bool retval = (want_parallel) ? m.LoadModulesParallel(std::thread::hardware_concurrency())
+                                  : m.LoadListedModules(!want_console);
     modules_loaded = m.GetModuleCount();
     if (modules_loaded > 0) {
         return retval;
@@ -285,11 +286,13 @@ int FirstStageMain(int argc, char** argv) {
     }
 
     auto want_console = ALLOW_FIRST_STAGE_CONSOLE ? FirstStageConsole(cmdline, bootconfig) : 0;
+    auto want_parallel =
+            bootconfig.find("androidboot.load_modules_parallel = \"true\"") != std::string::npos;
 
     boot_clock::time_point module_start_time = boot_clock::now();
     int module_count = 0;
     if (!LoadKernelModules(IsRecoveryMode() && !ForceNormalBoot(cmdline, bootconfig), want_console,
-                           module_count)) {
+                           want_parallel, module_count)) {
         if (want_console != FirstStageConsoleParam::DISABLED) {
             LOG(ERROR) << "Failed to load kernel modules, starting console";
         } else {

libmodprobe/include/modprobe/modprobe.h

@@ -16,17 +16,21 @@
 
 #pragma once
 
+#include <mutex>
 #include <set>
 #include <string>
 #include <unordered_map>
 #include <unordered_set>
 #include <vector>
 
+#include <android-base/thread_annotations.h>
+
 class Modprobe {
   public:
     Modprobe(const std::vector<std::string>&, const std::string load_file = "modules.load",
              bool use_blocklist = true);
 
+    bool LoadModulesParallel(int num_threads);
     bool LoadListedModules(bool strict = true);
     bool LoadWithAliases(const std::string& module_name, bool strict,
                          const std::string& parameters = "");
@@ -66,7 +70,9 @@ class Modprobe {
     std::vector<std::string> module_load_;
     std::unordered_map<std::string, std::string> module_options_;
     std::set<std::string> module_blocklist_;
+    std::mutex module_loaded_lock_;
     std::unordered_set<std::string> module_loaded_;
+    std::unordered_set<std::string> module_loaded_paths_;
     int module_count_ = 0;
     bool blocklist_enabled = false;
 };

libmodprobe/libmodprobe.cpp

@@ -21,8 +21,10 @@
 #include <sys/syscall.h>
 
 #include <algorithm>
+#include <map>
 #include <set>
 #include <string>
+#include <thread>
 #include <vector>
 
 #include <android-base/chrono_utils.h>
@@ -437,6 +439,97 @@ bool Modprobe::IsBlocklisted(const std::string& module_name) {
     return module_blocklist_.count(canonical_name) > 0;
 }
 
+// Another option to load kernel modules. load in independent modules in parallel
+// and then load modules which only have soft dependency, third update dependency list of other
+// remaining modules, repeat these steps until all modules are loaded.
+bool Modprobe::LoadModulesParallel(int num_threads) {
+    bool ret = true;
+    std::map<std::string, std::set<std::string>> mod_with_deps;
+    std::map<std::string, std::set<std::string>> mod_with_softdeps;
+
+    // Get dependencies
+    for (const auto& module : module_load_) {
+        auto dependencies = GetDependencies(MakeCanonical(module));
+
+        for (auto dep = dependencies.rbegin(); dep != dependencies.rend(); dep++) {
+            mod_with_deps[module].emplace(*dep);
+        }
+    }
+
+    // Get soft dependencies
+    for (const auto& [it_mod, it_softdep] : module_pre_softdep_) {
+        mod_with_softdeps[MakeCanonical(it_mod)].emplace(it_softdep);
+    }
+
+    // Get soft post dependencies
+    for (const auto& [it_mod, it_softdep] : module_post_softdep_) {
+        mod_with_softdeps[MakeCanonical(it_mod)].emplace(it_softdep);
+    }
+
+    while (!mod_with_deps.empty()) {
+        std::vector<std::thread> threads;
+        std::vector<std::string> mods_path_to_load;
+        std::vector<std::string> mods_with_softdep_to_load;
+        std::mutex vector_lock;
+
+        // Find independent modules and modules only having soft dependencies
+        for (const auto& [it_mod, it_dep] : mod_with_deps) {
+            if (it_dep.size() == 1 && mod_with_softdeps[it_mod].empty()) {
+                mods_path_to_load.emplace_back(*(it_dep.begin()));
+            } else if (it_dep.size() == 1) {
+                mods_with_softdep_to_load.emplace_back(it_mod);
+            }
+        }
+
+        // Load independent modules in parallel
+        auto thread_function = [&] {
+            std::unique_lock lk(vector_lock);
+            while (!mods_path_to_load.empty()) {
+                auto mod_path_to_load = std::move(mods_path_to_load.back());
+                mods_path_to_load.pop_back();
+
+                lk.unlock();
+                ret &= Insmod(mod_path_to_load, "");
+                lk.lock();
+            }
+        };
+
+        std::generate_n(std::back_inserter(threads), num_threads,
+                        [&] { return std::thread(thread_function); });
+
+        // Wait for the threads.
+        for (auto& thread : threads) {
+            thread.join();
+        }
+
+        // Since we cannot assure if these soft dependencies tree are overlap,
+        // we loaded these modules one by one.
+        for (auto dep = mods_with_softdep_to_load.rbegin(); dep != mods_with_softdep_to_load.rend();
+             dep++) {
+            ret &= LoadWithAliases(*dep, true);
+        }
+
+        std::lock_guard guard(module_loaded_lock_);
+        // Remove loaded module form mod_with_deps and soft dependencies of other modules
+        for (const auto& module_loaded : module_loaded_) {
+            mod_with_deps.erase(module_loaded);
+
+            for (auto& [mod, softdeps] : mod_with_softdeps) {
+                softdeps.erase(module_loaded);
+            }
+        }
+
+        // Remove loaded module form dependencies of other modules which are not loaded yet
+        for (const auto& module_loaded_path : module_loaded_paths_) {
+            for (auto& [mod, deps] : mod_with_deps) {
+                deps.erase(module_loaded_path);
+            }
+        }
+    }
+
+    return ret;
+}
+
 bool Modprobe::LoadListedModules(bool strict) {
     auto ret = true;
     for (const auto& module : module_load_) {

libmodprobe/libmodprobe_ext.cpp

@@ -54,6 +54,8 @@ bool Modprobe::Insmod(const std::string& path_name, const std::string& parameter
     if (ret != 0) {
         if (errno == EEXIST) {
             // Module already loaded
+            std::lock_guard guard(module_loaded_lock_);
+            module_loaded_paths_.emplace(path_name);
             module_loaded_.emplace(canonical_name);
             return true;
         }
@@ -62,6 +64,8 @@ bool Modprobe::Insmod(const std::string& path_name, const std::string& parameter
     }
 
     LOG(INFO) << "Loaded kernel module " << path_name;
+    std::lock_guard guard(module_loaded_lock_);
+    module_loaded_paths_.emplace(path_name);
     module_loaded_.emplace(canonical_name);
     module_count_++;
     return true;
@@ -74,6 +78,7 @@ bool Modprobe::Rmmod(const std::string& module_name) {
         PLOG(ERROR) << "Failed to remove module '" << module_name << "'";
         return false;
     }
+    std::lock_guard guard(module_loaded_lock_);
     module_loaded_.erase(canonical_name);
     return true;
 }

libmodprobe/libmodprobe_test.cpp

@@ -188,10 +188,11 @@ TEST(libmodprobe, Test) {
 
     EXPECT_TRUE(modules_loaded == expected_after_remove);
 
-    m = Modprobe({dir.path});
-    EXPECT_FALSE(m.LoadWithAliases("test4", true));
-    while (modules_loaded.size() > 0) EXPECT_TRUE(m.Remove(modules_loaded.front()));
-    EXPECT_TRUE(m.LoadListedModules());
+    Modprobe m2({dir.path});
+
+    EXPECT_FALSE(m2.LoadWithAliases("test4", true));
+    while (modules_loaded.size() > 0) EXPECT_TRUE(m2.Remove(modules_loaded.front()));
+    EXPECT_TRUE(m2.LoadListedModules());
 
     GTEST_LOG_(INFO) << "Expected modules loaded after enabling blocklist (in order):";
     for (auto i = expected_modules_blocklist_enabled.begin();