Re: concurrent garbage collection and POSIX threads

--- On Tue, 1/5/10, Rafael R. Sevilla <[email protected]> wrote:

> From: Rafael R. Sevilla <[email protected]>
> Subject: [gclist] concurrent garbage collection and POSIX threads
> To: [email protected]
> Received: Tuesday, January 5, 2010, 10:14 PM
> I'm attempting to implement a
> concurrent garbage collector (specifically
> the Huelsbergen-Winterbottom VCGC algorithm) for a small
> compiled
> language I'm working on and they it requires that one be
> able to pause
> execution of all running threads during a barrier
> synchronization event
> at the end of a garbage collection epoch, and then resume
> execution of
> these threads afterwards.=C2=A0 I believe many other
> concurrent garbage
> collection algorithms have similar requirements.=C2=A0 How
> would one
> implement this using POSIX.1b/1c primitives alone?=C2=A0
> The pause and resume
>=C2=A0 are in general asynchronous.=C2=A0 I've thought up a
> rather convoluted
> method that involves adding a signal handler for each
> thread, which upon
> receipt of a POSIX real time signal, does a wait on a
> condition
> variable.=C2=A0 When the thread is to be resumed, the
> condition variable is
> signaled, causing all threads waiting on it to resume
> execution, at
> which point the signal handler returns and execution
> resumes.
>=20
> I wonder if there is an easier way to do this that does not
> require
> these kinds of contortions.=C2=A0=C2=A0=C2=A0There are
> thr_suspend/thr_resume calls in
> Solaris, and in older versions of Linux using LinuxThreads
> it was
> possible to use SIGSTOP/SIGCONT on the thread ID, but with
> NPTL, which
> is now fully POSIX-compliant, the use of those signal would
> stop all
> threads, which I do not want.=C2=A0 Any hints from those
> who have implemented
> such garbage collectors?
>=20
> --=20
> =E5=AD=98=E5=9C=A8=E3=81=99=E3=82=8B=E3=81=A8=E3=81=84=E3=81=86=E3=81=93=
=E3=81=A8=E3=81=AF=E3=80=81=E8=87=AA=E5=88=86=E3=82=92=E5=89=B5=E9=80=A0=E3=
=81=99=E3=82=8B=E3=81=93=E3=81=A8=E3=81=A0=E3=80=82
> http://stormwyrm.blogspot.com
>=20
>

You don't have to pause any execution of app threads for a concurrent garba=
ge collector. A full concurrent garbage collector can run as a lowest prior=
ity thread, and never invoke any thr_suspend/resume the like calls.

- Mingnan Guo