On Jan 31, 2006, at 3:51 PM, Dalibor Topic wrote:
On Tue, 2006-01-31 at 22:00 +0100, Roman Kennke wrote:
Granted,
Aicas is a commercial party and cannot publish every port. There
is also
Kaffe, which is 100% GPL and now also suggest something similar
like the
target layer, only somewhat nicer, and again it seems to turn out
to be
a fight against windmills.
A major issue is that for green threads (i.e. jthreads) in Kaffe, we'd
have to make sure that we can disable interrupts before invoking a
system method, and enable them before we exit again. If we don't do
that, than bad things can (and do ;) happen.
That's a pretty Kaffe-specific need, though, so it may not make
sense to
make room for it in GNU Classpath, unless it is accompanied by some
other, instant gratification, like looking very much like plain old
POSIX. In theory, if we're lucky, Kaffe may also be able to get by
using
AspectC++[1] or something equivalently weird to weave in the stuff we
need for jthreads. In practice, I don't think anyone has done
something
like that yet, though. ;)
Would it help to have a utility function, say as a private function
in the JNIEnv, that told the VM that the code was entering or just
exited a possibly-blocking system call? Which, in the default
implementation for other VMs or threading systems, would be a no-op?
E.g.:
void EnterSystemCall (JNIEnv *env, void *address);
void ExitSystemCall (JNIEnv *env, void *address);
This would (I think) be a good place for Kaffe to disable whatever
interrupts it had to, and would still be a generic-enough mechanism
for a VM to keep track of where the native code is. We would need to
find all the right places to call this, but I don't think that's much
harder than rewriting everything with wrapper functions, and it would
be extensible -- anything added that Kaffe needed to tweak on before
calling would be made safe, as long as the usage was consistent.
