Monitor destructor...

[Keith McGuigan]

Whoops, I take it back - I didn't notice that ClearMonitor() sets this->_name. 
Ignore my last message...

--
- Keith

Keith McGuigan wrote:
> Peter -
> 
> Just a guess here, but I see that there's two constructors for Mutex(), 
> one which sets _name to what you want, but the other one (the no-arg 
> one) doesn't appear to initialize _name at all.  If you have a Mutex 
> that was created via that constructor, _name will be junk and your 
> deallocation in the desstructor will fail.  (By the way, what you have 
> works but it would probably be better to deallocate the memory with 
> FREE_C_HEAP_ARRAY(char,_name), to keep the name pairing).
> 
> -- 
> - Keith
> 
> Peter Helfer wrote:
>> Hi all
>>
>> I've got some funny error I'm running into: In order to see what 
>> deadlocks I'm creating, I extended the Monitor (Mutex) constructor to 
>> copy the "name" parameter, instead of keeping it at "UNKNOWN" (as of 
>> ClearMonitor).
>>
>> class Monitor{
>> ...
>> char * _name;                    // Name of mutex REMOVED const!
>> ..
>> };
>> static const char* Monitor::_default = "UNKNOWN";
>>
>>
>> void Monitor::ClearMonitor (Monitor * m) {
>>   m->_owner             = NULL ;
>>   m->_snuck             = false ;
>>   m->_name              = (char*) Monitor::_default;
>>   m->_LockWord.FullWord = 0 ;
>>   m->_EntryList         = NULL ;
>>   m->_OnDeck            = NULL ;
>>   m->_WaitSet           = NULL ;
>>   m->_WaitLock[0]       = 0 ;
>> }
>>
>> Monitor::Monitor() { ClearMonitor(this); }
>>
>> Monitor::Monitor (int Rank, const char * name, bool allow_vm_block) {
>>   ClearMonitor (this) ;
>> #ifdef ASSERT
>>   if(name){
>>         int len            = strnlen(name,63);
>>         _name              = NEW_C_HEAP_ARRAY(char,len+1);
>>         assert(_name, "Not enough mem");
>>         strncpy(_name, name, len+1);
>>   }
>>   _allow_vm_block  = allow_vm_block;
>>   _rank            = Rank ;
>> #endif
>> }
>>
>> Monitor::~Monitor() {
>>   assert 
>> ((UNS(_owner)|UNS(_LockWord.FullWord)|UNS(_EntryList)|UNS(_WaitSet)|UNS(_OnDeck)) 
>> == 0, "") ;
>>   #ifdef ASSERT
>>   if(_name != _default){
>>         FreeHeap(_name);
>>   }
>>   #endif
>> }
>>
>> This is what I am seeing: it only doesnt work in this situation.. The 
>> easy work around is to remove the code again, but thats actually not 
>> the idea.. :-)
>>
>> /home/peterh/workspace/openjdk/control/build/linux-i586-debug/bin/java 
>> -client -Xmx881m -Xms128m -XX:PermSize=32m -XX:MaxPermSize=160m 
>> -classpath 
>> /home/peterh/workspace/openjdk/control/build/linux-i586-debug/tmp/meta-index 
>> BuildMetaIndex -o meta-index *.jar
>> VM option 'PermSize=32m'
>> VM option 'MaxPermSize=160m'
>> ## nof_mallocs = 19744, nof_frees = 12802
>> ## memory stomp: byte at 0x8189648 in front of object 0x8189660
>> ### previous object (not sure if correct): 0x8189648 (73 bytes)
>> ### next object (not sure if correct): 0x8189694 (1700358998 bytes)
>> # To suppress the following error report, specify this argument
>> # after -XX: or in .hotspotrc:  SuppressErrorAt=/os.cpp:544
>> #
>> # An unexpected error has been detected by Java Runtime Environment:
>> #
>> #  Internal Error 
>> (/home/peterh/workspace/openjdk/hotspot/src/share/vm/runtime/os.cpp:544), 
>> pid=7146, tid=2209852304
>> #  Error: memory stomping error
>> #
>>