From: Blaisorblade <blaisorblade_spam@yahoo.it>
To: Daniel Jacobowitz <dan@debian.org>
Subject: Re: Fixing UML against NPTL (was: Re: [uml-devel] [PATCH] UML: Use PTRACE_KILL instead of SIGKILL to kill host-OS processes (take #2))
Date: Fri, 12 Nov 2004 01:09:02 +0100
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Cc: Christophe Saout <christophe@saout.de>, Chris Wedgwood <cw@f00f.org>,
       LKML <linux-kernel@vger.kernel.org>
References: <20041103113736.GA23041@taniwha.stupidest.org> <1100197911.11951.1.camel@leto.cs.pocnet.net> <20041111184523.GA11578@nevyn.them.org>
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On Thursday 11 November 2004 19:45, Daniel Jacobowitz wrote:
> On Thu, Nov 11, 2004 at 07:31:51PM +0100, Christophe Saout wrote:
> > Am Donnerstag, den 11.11.2004, 12:45 -0500 schrieb Daniel Jacobowitz:
> > > Glibc caches the PID.  If you're going to use clone directly, use the
> > > gettid/getpid syscall directly.  It's kind of rude that glibc breaks
> > > getpid in this way; I recommend filing a bug in the glibc bugzilla at
> > > sources.redhat.com.
>
> ... but, thinking about it, they'll probably close it as INVALID.
>
> > If glibc insists on caching the pid, it could also simply invalidate the
> > pid cache in the clone function.

> It currently does this for vfork, but not clone.  Basically, you can't
> call into glibc at all if you use clone.  If you aren't using POSIX
> threads, then the POSIX-compliant library is going to fall to pieces
> around you.  For instance, all the file locking will break, and
> anything else that, like the PID cache, relies on either global or
> per-_thread_ data.

Yes, in fact I guess that the problem is for any _thread variable. And as 
fork() is not a raw syscall, so clone() shouldn't be.

I'll file a bugreport when I have time to do it properly - I don't want to 
hear that "if I go into dirty things using clone(), I get to keep the pieces 
and setup a different TLS for the new process"
-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729
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