Request for review: 7046490 - Preallocated OOME objects should obey Throwable stack trace protocol

[Thomas Rodriguez]

You can use ik->java_mirror()->obj_field(offset) to read static fields. I don't know why the others are done as they are. maybe just history. 

tom

On Jul 18, 2011, at 9:02 PM, David Holmes <David.Holmes at oracle.com> wrote:

> Paul Hohensee said the following on 07/19/11 13:32:
>> Looks good, except, could you use obj_field() in unassigned_stacktrace() instead of checking UseCompressedOops there?
> 
> Thanks Paul.
> 
> I don't think I can use obj_field() as it is for accessing instances and this is a static field. I copied the code for reading the static field from the java.lang.ref functions:
> 
> 2286 // Support for java_lang_ref_Reference
> 2287 oop java_lang_ref_Reference::pending_list_lock() {
> 2288   instanceKlass* ik = instanceKlass::cast(SystemDictionary::Reference_klass());
> 2289   address addr = ik->static_field_addr(static_lock_offset);
> 2290   if (UseCompressedOops) {
> 2291     return oopDesc::load_decode_heap_oop((narrowOop *)addr);
> 2292   } else {
> 2293     return oopDesc::load_decode_heap_oop((oop*)addr);
> 2294   }
> 2295 }
> 2296
> 2297 HeapWord *java_lang_ref_Reference::pending_list_addr() {
> 2298   instanceKlass* ik = instanceKlass::cast(SystemDictionary::Reference_klass());
> 2299   address addr = ik->static_field_addr(static_pending_offset);
> 2300   // XXX This might not be HeapWord aligned, almost rather be char *.
> 2301   return (HeapWord*)addr;
> 2302 }
> 2303
> 2304 oop java_lang_ref_Reference::pending_list() {
> 2305   char *addr = (char *)pending_list_addr();
> 2306   if (UseCompressedOops) {
> 2307     return oopDesc::load_decode_heap_oop((narrowOop *)addr);
> 2308   } else {
> 2309     return oopDesc::load_decode_heap_oop((oop*)addr);
> 2310   }
> 2311 }
> 
> David
> -----
> 
>> Paul
>> On 7/7/11 1:25 AM, David Holmes wrote:
>>> http://cr.openjdk.java.net/~dholmes/7046490/webrev/
>>> 
>>> This is a simple fix in the VM to honour the Throwable immutability protocol that was defined for Java 7. Pre-allocated Throwable instances are normally immutable, but that is not the case for a group of pre-allocated OutOfMemoryError instances. To conform to the protocol, when we set the backtrace (VM representation of the stackTrace) we have to set the stackTrace field to the sentinel value stored in the static Throwable.UNASSIGNED_STACK field.
>>> 
>>> With this fix in place the workaround in Throwable.java, under 7045138, can be backed out.
>>> 
>>> Thanks,
>>> David
>>> 
>>> 
>>>