Revert "Prevent agents from delaying system daemon threads"

This reverts commit 3611fdf703a6417c08a2e3d6e642d5936318de18.

Bug: 123696564
Bug: 124284724
Reason for revert: b/124284724

Change-Id: I546758b4cbb5e3f62f7b66a2faed544abce0d9c2

6 files changed, 5 insertions, 59 deletions

diff --git a/openjdkjvmti/ti_thread.cc b/openjdkjvmti/ti_thread.cc
index 1021648a2c..051db4c67e 100644
--- a/openjdkjvmti/ti_thread.cc
+++ b/openjdkjvmti/ti_thread.cc
@@ -47,7 +47,6 @@
 #include "mirror/class.h"
 #include "mirror/object-inl.h"
 #include "mirror/string.h"
-#include "mirror/throwable.h"
 #include "nativehelper/scoped_local_ref.h"
 #include "nativehelper/scoped_utf_chars.h"
 #include "obj_ptr.h"
@@ -84,17 +83,6 @@ struct ThreadCallback : public art::ThreadLifecycleCallback {
   }
 
   void ThreadStart(art::Thread* self) override REQUIRES_SHARED(art::Locks::mutator_lock_) {
-    // Needs to be checked first because we might start these threads before we actually send the
-    // VMInit event.
-    if (self->IsSystemDaemon()) {
-      // System daemon threads are things like the finalizer or gc thread. It would be dangerous to
-      // allow agents to get in the way of these threads starting up. These threads include things
-      // like the HeapTaskDaemon and the finalizer daemon.
-      //
-      // This event can happen during the time before VMInit or just after zygote fork. Since the
-      // second is hard to distinguish we unfortunately cannot really check the state here.
-      return;
-    }
     if (!started) {
       // Runtime isn't started. We only expect at most the signal handler or JIT threads to be
       // started here.
@@ -144,35 +132,16 @@ void ThreadUtil::VMInitEventSent() {
   gThreadCallback.Post<ArtJvmtiEvent::kThreadStart>(art::Thread::Current());
 }
 
-
-static void WaitForSystemDaemonStart(art::Thread* self) REQUIRES_SHARED(art::Locks::mutator_lock_) {
-  {
-    art::ScopedThreadStateChange strc(self, art::kNative);
-    JNIEnv* jni = self->GetJniEnv();
-    jni->CallStaticVoidMethod(art::WellKnownClasses::java_lang_Daemons,
-                              art::WellKnownClasses::java_lang_Daemons_waitForDaemonStart);
-  }
-  if (self->IsExceptionPending()) {
-    LOG(WARNING) << "Exception occured when waiting for system daemons to start: "
-                 << self->GetException()->Dump();
-    self->ClearException();
-  }
-}
-
 void ThreadUtil::CacheData() {
   // We must have started since it is now safe to cache our data;
   gThreadCallback.started = true;
-  art::Thread* self = art::Thread::Current();
-  art::ScopedObjectAccess soa(self);
+  art::ScopedObjectAccess soa(art::Thread::Current());
   art::ObjPtr<art::mirror::Class> thread_class =
       soa.Decode<art::mirror::Class>(art::WellKnownClasses::java_lang_Thread);
   CHECK(thread_class != nullptr);
   context_class_loader_ = thread_class->FindDeclaredInstanceField("contextClassLoader",
                                                                   "Ljava/lang/ClassLoader;");
   CHECK(context_class_loader_ != nullptr);
-  // Now wait for all required system threads to come up before allowing the rest of loading to
-  // continue.
-  WaitForSystemDaemonStart(self);
 }
 
 void ThreadUtil::Unregister() {
diff --git a/runtime/runtime.cc b/runtime/runtime.cc
index 7ecfdc70cd..1465b14d44 100644
--- a/runtime/runtime.cc
+++ b/runtime/runtime.cc
@@ -869,22 +869,15 @@ bool Runtime::Start() {
                             GetInstructionSetString(kRuntimeISA));
   }
 
-  StartDaemonThreads();
-
-  // Make sure the environment is still clean (no lingering local refs from starting daemon
-  // threads).
-  {
-    ScopedObjectAccess soa(self);
-    self->GetJniEnv()->AssertLocalsEmpty();
-  }
-
-  // Send the initialized phase event. Send it after starting the Daemon threads so that agents
-  // cannot delay the daemon threads from starting forever.
+  // Send the initialized phase event. Send it before starting daemons, as otherwise
+  // sending thread events becomes complicated.
   {
     ScopedObjectAccess soa(self);
     callbacks_->NextRuntimePhase(RuntimePhaseCallback::RuntimePhase::kInit);
   }
 
+  StartDaemonThreads();
+
   {
     ScopedObjectAccess soa(self);
     self->GetJniEnv()->AssertLocalsEmpty();
diff --git a/runtime/thread.cc b/runtime/thread.cc
index 44b45cfa75..4828aaef2c 100644
--- a/runtime/thread.cc
+++ b/runtime/thread.cc
@@ -4258,12 +4258,4 @@ int Thread::GetNativePriority() {
   return priority;
 }
 
-bool Thread::IsSystemDaemon() const {
-  if (GetPeer() == nullptr) {
-    return false;
-  }
-  return jni::DecodeArtField(
-      WellKnownClasses::java_lang_Thread_systemDaemon)->GetBoolean(GetPeer());
-}
-
 }  // namespace art
diff --git a/runtime/thread.h b/runtime/thread.h
index ec276b59f5..7a14fd7b48 100644
--- a/runtime/thread.h
+++ b/runtime/thread.h
@@ -1230,8 +1230,6 @@ class Thread {
     return this == jit_sensitive_thread_;
   }
 
-  bool IsSystemDaemon() const REQUIRES_SHARED(Locks::mutator_lock_);
-
   // Returns true if StrictMode events are traced for the current thread.
   static bool IsSensitiveThread() {
     if (is_sensitive_thread_hook_ != nullptr) {
diff --git a/runtime/well_known_classes.cc b/runtime/well_known_classes.cc
index 19fbf63ff5..955a455d36 100644
--- a/runtime/well_known_classes.cc
+++ b/runtime/well_known_classes.cc
@@ -92,7 +92,6 @@ jmethodID WellKnownClasses::java_lang_ClassLoader_loadClass;
 jmethodID WellKnownClasses::java_lang_ClassNotFoundException_init;
 jmethodID WellKnownClasses::java_lang_Daemons_start;
 jmethodID WellKnownClasses::java_lang_Daemons_stop;
-jmethodID WellKnownClasses::java_lang_Daemons_waitForDaemonStart;
 jmethodID WellKnownClasses::java_lang_Double_valueOf;
 jmethodID WellKnownClasses::java_lang_Float_valueOf;
 jmethodID WellKnownClasses::java_lang_Integer_valueOf;
@@ -133,7 +132,6 @@ jfieldID WellKnownClasses::java_lang_Thread_lock;
 jfieldID WellKnownClasses::java_lang_Thread_name;
 jfieldID WellKnownClasses::java_lang_Thread_priority;
 jfieldID WellKnownClasses::java_lang_Thread_nativePeer;
-jfieldID WellKnownClasses::java_lang_Thread_systemDaemon;
 jfieldID WellKnownClasses::java_lang_Thread_unparkedBeforeStart;
 jfieldID WellKnownClasses::java_lang_ThreadGroup_groups;
 jfieldID WellKnownClasses::java_lang_ThreadGroup_ngroups;
@@ -353,7 +351,6 @@ void WellKnownClasses::Init(JNIEnv* env) {
 
   java_lang_Daemons_start = CacheMethod(env, java_lang_Daemons, true, "start", "()V");
   java_lang_Daemons_stop = CacheMethod(env, java_lang_Daemons, true, "stop", "()V");
-  java_lang_Daemons_waitForDaemonStart = CacheMethod(env, java_lang_Daemons, true, "waitForDaemonStart", "()V");
   java_lang_invoke_MethodHandles_lookup = CacheMethod(env, "java/lang/invoke/MethodHandles", true, "lookup", "()Ljava/lang/invoke/MethodHandles$Lookup;");
   java_lang_invoke_MethodHandles_Lookup_findConstructor = CacheMethod(env, "java/lang/invoke/MethodHandles$Lookup", false, "findConstructor", "(Ljava/lang/Class;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/MethodHandle;");
 
@@ -388,7 +385,6 @@ void WellKnownClasses::Init(JNIEnv* env) {
   java_lang_Thread_name = CacheField(env, java_lang_Thread, false, "name", "Ljava/lang/String;");
   java_lang_Thread_priority = CacheField(env, java_lang_Thread, false, "priority", "I");
   java_lang_Thread_nativePeer = CacheField(env, java_lang_Thread, false, "nativePeer", "J");
-  java_lang_Thread_systemDaemon = CacheField(env, java_lang_Thread, false, "systemDaemon", "Z");
   java_lang_Thread_unparkedBeforeStart = CacheField(env, java_lang_Thread, false, "unparkedBeforeStart", "Z");
   java_lang_ThreadGroup_groups = CacheField(env, java_lang_ThreadGroup, false, "groups", "[Ljava/lang/ThreadGroup;");
   java_lang_ThreadGroup_ngroups = CacheField(env, java_lang_ThreadGroup, false, "ngroups", "I");
diff --git a/runtime/well_known_classes.h b/runtime/well_known_classes.h
index 3c5144fbd5..872b562bd5 100644
--- a/runtime/well_known_classes.h
+++ b/runtime/well_known_classes.h
@@ -101,7 +101,6 @@ struct WellKnownClasses {
   static jmethodID java_lang_ClassNotFoundException_init;
   static jmethodID java_lang_Daemons_start;
   static jmethodID java_lang_Daemons_stop;
-  static jmethodID java_lang_Daemons_waitForDaemonStart;
   static jmethodID java_lang_Double_valueOf;
   static jmethodID java_lang_Float_valueOf;
   static jmethodID java_lang_Integer_valueOf;
@@ -142,7 +141,6 @@ struct WellKnownClasses {
   static jfieldID java_lang_Thread_name;
   static jfieldID java_lang_Thread_priority;
   static jfieldID java_lang_Thread_nativePeer;
-  static jfieldID java_lang_Thread_systemDaemon;
   static jfieldID java_lang_Thread_unparkedBeforeStart;
   static jfieldID java_lang_ThreadGroup_groups;
   static jfieldID java_lang_ThreadGroup_ngroups;