RFR: 8330027: Identity hashes of archived objects must be based on a reproducible random seed [v3]

[Thomas Stuefe]

On Mon, 22 Apr 2024 00:23:18 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> > I get that the chance for this happening is remote, but hunting sources of entropy is frustrating work, and the patch is really very simple. So, why not fix it? I don't share the opinion that this is added complexity.
> 
> Why not do it inside `Thread::Thread()`
> 
> ```
> // thread-specific hashCode stream generator state - Marsaglia shift-xor form
>   if (CDSConfig::is_dumping_static_archive()) {
>      _hashStateX = 0;
>   } else {
>      _hashStateX = os::random();
>   }  
> ```

Because then it would inject `os::random` into the startup of every thread, not just of every thread that generates iHashes. So it would also fire for GC threads and other thread started before "our" threads. That would make our random sequence vulnerable against order and number of threads started.

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PR Comment: https://git.openjdk.org/jdk/pull/18735#issuecomment-2068515287