[RFC]: Linkage Error fix.

[Andrew Haley]

On 04/18/2011 06:48 PM, Deepak Bhole wrote:
> * Dr Andrew John Hughes <ahughes at redhat.com> [2011-04-18 13:10]:
>> On 09:45 Mon 18 Apr     , Andrew Haley wrote:
>>> On 15/04/11 20:55, Deepak Bhole wrote:
>>>
>>>> Did you look into how URLCloassLoader and others mitigate the problem?
>>>> If I am not mistaken, all class load requests go through JNLPClassLoader,
>>>> and synchronizing on each such call can get expensive.
>>>
>>> In 1.6 ClassLoader.loadClass() is a synchronized method anyway.
>>>
>>> There's something of a myth about the expense of synchronization that
>>> isn't usually justified by actual measurements.  It's usually only a
>>> compareAndSwap, and there is little pain for uncontended cases.
>>> Avoiding synchronization with more complex schemes may actually be
>>> slower; you have to measure it.
>>>
>>
>> Be correct first.  Only then worry about performance.
> 
> Replying here for this message:
> 
> http://mail.openjdk.java.net/pipermail/distro-pkg-dev/2011-April/013664.html
> 
> The new patch synchronizes all of loadClass. I am against this
> approach with the current design. 
> 
> The latter part of loadClass() connects to remote sites to download
> additional jars. Networks are unreliable and synchronizing a critical
> method like loadClass knowing it can get delayed on network is a bad
> idea IMO.
> 
> That is one of the reasons I suggested studying how URLClassLoader does
> it.. it too has to deal with remote connectivity for loading, so it
> probably has a cleaner solution for this.

You can call getResource, which doesn't need locking, and then call
defineClass(name, resource) only once you have the bytes.

Andrew.