[vmkit-commits] [PATCH] OpenJDK threading: initialize fields

[Will Dietz]

Inlined below.

The main thing is the small change to explicitly set the eetop field
to the JavaThread.

The reason we set the fields *before* calling the constructor is due
to a bit of strangeness that probably needs some discussion.

In the thread constructor, it defaults to setting the
thread-being-constructed's priority and daemon status from what the
parent thread has for those values.  The parent thread is determined
by a call to JVM_CurrentThread.

This is all well and good except when we're using CreateJavaThread to
create the Thread for the currently-running main thread, since this
means the constructor will try to use the values of the thread it's
mid-creating to initialize itself with.  And of course it does sanity
checks on those values and things don't work out well (turns out '0'
is an invalid priority).

I thought about making this specific to the main thread construction,
but it doesn't seem worth it since in all other cases these values
will be overridden happily immediately anyway.

I understand this is a tad hacky, but the alternatives I thought of
seemed worse (some kinda of placeholder parent-of-main thread whose
sole purpose in existing is to fix this field initialization issue).

As always thoughts very much welcome, and thank you for your time :).

~Will

>From 2dc1fa5b0da33852cfca80b67e50967d0262709a Mon Sep 17 00:00:00 2001
From: Will Dietz <w at wdtz.org>
Date: Thu, 27 Oct 2011 19:29:48 -0500
Subject: [PATCH 4/8] OpenJDK threading: intialize fields, set eeetop field.

---
 lib/J3/ClassLib/OpenJDK/JavaUpcalls.cpp |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/lib/J3/ClassLib/OpenJDK/JavaUpcalls.cpp
b/lib/J3/ClassLib/OpenJDK/JavaUpcalls.cpp
index 476b6e3..d9fa7d7 100644
--- a/lib/J3/ClassLib/OpenJDK/JavaUpcalls.cpp
+++ b/lib/J3/ClassLib/OpenJDK/JavaUpcalls.cpp
@@ -235,12 +235,16 @@ void Classpath::CreateJavaThread(Jnjvm* vm,
JavaThread* myth,

   name = vm->asciizToStr(thName);

+  // Initialize the values
+  priority->setInstanceInt32Field(th, (uint32)5);
+  daemon->setInstanceInt8Field(th, (uint32)false);
+
   // call Thread(ThreadGroup,String) constructor
   initThread->invokeIntSpecial(vm, newThread, th, &Group, &name);

   // Store reference to the JavaThread for this thread in the 'eetop' field
-  // TODO: Don't do this until we have the tracing handled.
-  // eetop->setInstanceLongField(th, (long)myth);
+  // GC-safe since 'eetop' is of type 'long'
+  eetop->setInstanceLongField(th, (long)myth);
 }

 void Classpath::InitializeThreading(Jnjvm* vm) {
-- 
1.7.5.1