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Re: gcj crashes if a user-thread gives up its rights
- From: Jost Boekemeier <jost2345 at yahoo dot de>
- To: Hans Boehm <Hans dot Boehm at hp dot com>, Chris Gray <chris dot gray at kiffer dot be>
- Cc: java at gcc dot gnu dot org
- Date: Sun, 12 Dec 2004 19:48:12 +0100 (CET)
- Subject: Re: gcj crashes if a user-thread gives up its rights
> My impression is that setuid is really intended to
> effect the whole process, not just a thread
As far as I can tell all modern thread implemtations
NPTL, BSD which I've tested change the permissions for
the current thread, only. Everything else would not
make much sense, imho.
> You are relying on a violation of the applicable
> standards.
Not sure if that was ever a standard or documented
anywhere. Applying the limited rights to all threads
would be useless; the only reason we've started the
new thread is to drop the rights for this session.
Dropping the rights for all threads would trash the
whole java application.
> That aside, the garbage collector may currently run
> in any thread that allocates from the Java heap.
That makes sense. An old version of the IBM JDK
(1.4.1) has had the same problem. Since 1.4.2_02 and
the recent Sun JDK's this problem doesn't appear
anymore.
> Also Linuxthreads makes heavy use of signals
> internally for various
No. Linux threads and NPTL work correctly. The issue
is a gcj/GC issue, only.
I think it may be possible to fix the problem in the
gc by using a different IPC mechanism instead of
sending a signal. I will take a look at this when I
have some time.
Jost
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