Re: [Sablevm-developer] acquiring monitor

[Etienne M. G. <eti...@uq...>]

Hi David,

Archie is right; synchronization is needed to avoid creating more than
one Method instance.

In fact, all class-loader related code that either reads or writes
class-loader data structures has to be synchronized using the monitor
of the VirtualMachine class instance.

In particular, calling _svmf_resolve_incomplete_method() without
synchronization would yield undefined results.  Furthermore, as Archie
pointer, we definitely do not want another thread to create an
instance between the:

   if (method_info->reflection_instance != NULL)
   ...

and the
  
   ...
   *(method_info->reflection_instance) = *method;

Doing otherwise would (among other things) leak memory.

Have fun!

Etienne

On Sun, Feb 09, 2003 at 09:05:22PM -0800, Archie Cobbs wrote:
> David Paul BELANGER wrote:
> > > In the case of Class.getMethod() (and therefore Class.nativeGetMethod())
> > > the spec says that accessing the Method object associated with a
> > > class is an "active use" and so the class must be linked if it hasn't
> > > already been linked. And linking the class's type of course requires
> > > acquiring the monitor.
> > 
> > Yes, I do understand that part but the link functions do acquire it.
> > I am wondering why we have this structure:
> > 
> > acquire monitor
> > .
> > .
> > .
> > link_class()
> >   (inside link_class)
> >   acquire monitor
> >   .
> >   .
> >   .
> >   release monitor
> > .
> > initialize_class
> >   acquire monitor
> >   .
> >   .
> >   release monitor
> > .
> > .
> > release monitor
> > 
> > What functions are we protecting with the external acquire monitor?
> 
> Maybe it's for the creation of the new Method reflection instance?
> The JVM must ensure that it only gets created once.
> 
> -Archie
> 
> __________________________________________________________________________
> Archie Cobbs     *     Packet Design     *     http://www.packetdesign.com
> 
> 
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-- 
Etienne M. Gagnon, Ph.D.             http://www.info.uqam.ca/~egagnon/
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