On 09/09/2016 11:26 AM, Alan Bateman wrote:
On 08/09/2016 23:29, David M. Lloyd wrote:
Is it not necessary that any class loader in use by a Layer must be
parallel-capable? Otherwise it seems like deadlocks could occur in
certain situations when there are references that are cyclic with
respect to class loaders mapped by the mapping function.
There aren't cycles in readability graph, at least not at construction
time. They might arise later due to reflective use of addReads but that
shouldn't change the class loader delegation graph. So I'm curious if
you are actually running into an issue or not? I can easily come up with
a mapping to loaders to force this but it would be unusual mapping.
BTW: I'm not opposed to exposing isParallelCapable, just curious if this
is something that you are actually running into or not.
No, I've only run into this with our module system which is separate
from Jigsaw, but I was examining this code recently and I was surprised
to see that Jigsaw did not take this into account.
I don't think there needs to be a readability cycle between modules for
this to be a potential problem; there only has to be a cycle between
class loaders. So if you (for whatever reason) put half of your modules
in one class loader and half in another, and those modules refer to one
another, I think you might have a problem if those modules refer to one
another and the class loaders are not parallel capable. But like I said
that's just a hypothesis.
--
- DML
