Re: [RFC] GC: external thread suspension

[Keith Seitz <keiths at redhat dot com>]

Bryce McKinlay wrote:

> If the JDWP back-end is partially written in Java, then it is important 
> that GC can run when threads are suspended. If not, the back-end will be 
> prone to deadlock during memory allocation.

Is this true, though? JDWP does not suspend it own threads -- ever. All 
the Classpath JDWP threads are in their own ThreadGroup, and the 
debugger cannot suspend them, even if it asks to suspend everything.

The real question is, when a program thread is stopped, does it matter 
that the garbage collector cannot GC *on that thread* -- it can still GC 
any other active thread.

> I like how GC_suspend_self and GC_suspend_thread are handled in the same 
> way in this patch, however. Perhaps the two approaches can be combined?

I hadn't thought about this possibility. And unfortunately, I have to 
run for the day. I'll brood over it tonight and see what comes of it in 
the morning.

Thank you for reviewing this.

Keith