Casey Marshall wrote:
On Jan 31, 2006, at 6:10 PM, David P Grove wrote:
Jikes RVM also does m-to-n threading, so it's there's more than 1 VM
that's whacky in this regard. The things we need to do are most likely
different than what Kaffe needs to do, but having a chance to inject
a VM
callback before the thread dives off into a blocking system call is
something we would like to be able to do. We have some linux specific
hacks (evil with dlopen to intercept poll, select, etc), but it's
fragile
and doesn't work on other platforms like AIX and OS X that Jikes RVM
runs
on.
Would my suggestion for Enter/Exit callbacks help this?
Though enter/exit callbacks may help for a few syscalls but it won't for
some (like blocking read/write). For these new calls you need handle
blocking queues in the VM thread scheduler. That needs to put the fd
into non-blocking mode and when you do a read you first check if there
is any data (in non-blocking mode) and if there is not data then the
thread system queues the current thread and tells the scheduler to jump
somewhere else until some datas are available on the specified fd. So we
must really stick to rerouting a few IOs. I am sure that handling m-to-n
threading system is as difficult as what we are doing (maybe more).
Regards,
Guilhem.
