[Opensim-dev] .NET / Mono lock(obj) statement

[Justin Clark-Casey]

Homer Horwitz wrote:
> Hi Diva,
> 
> On Wed, Jan 14, 2009 at 5:57 AM, Diva Canto <diva at metaverseink.com> wrote:
>> Here's a simplified version of the problem:
>>
>> lock (a)
>> {
>>   foo();
>> }
>>
>> void foo()
>> {
>>  lock (a)
>>  {
>>    ...
>>  }
>> }
> I just tried that with Mono 2.0.1, and it works correctly (i.e. it
> doesn't deadlock). I used an instance variable object a = new object()
> for the lock.
> 

Yeah that is odd.  If mono had a general bug of this nature then OpenSim would lock up almost immediately after starting 
(well, some may say that it does this anyway (joke!)).

I don't think that we can remove locking long term as done in r8041.  On a strict reading of the Dictionary class 
definition, this operation is not thread safe.  And I've heard that this is actually the case in the underlying bytecode 
(an addition/removal operation could change the index whilst the code is within the indexing operation).  Even if it 
isn't, this isn't something that we should rely on.

>> (the real situation is a bit more complicated; foo() involves a
>> delegate; but ignore that)
> Is this maybe necessary to get the (wrong) result? Or did you use
> another Mono version?
> 
> Cheers,
>   Homer
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> 


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justincc
Justin Clark-Casey
http://justincc.wordpress.com