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List:       user-mode-linux-devel
Subject:    Re: [uml-devel] UML and Preemtive kernel patch on host
From:       Robert Love <rml () tech9 ! net>
Date:       2001-09-25 1:40:44
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On Mon, 2001-09-24 at 19:22, Will Dyson wrote:
> Jeff and Robert,
> 
> The problem I was having running UML under the preemptive host kernel 
> has been solved by applying Robert's ptrace-and-jobs-fix-2 patch to the 
> host kernel.
> 
> And its a good thing, since I only managed to get one stack crawl so far 
> of the hanging process on boot (hung on line 33 of signal_user.c, btw).

Great.  Glad to kill so many side-effects with that one stone.

> See this post on LKML:
> <http://www.uwsg.indiana.edu/hypermail/linux/kernel/0109.2/1549.html>
> 
> It actually makes some sense (in retrospect) that it was a problem with 
> ptrace, since UML uses ptrace to trap syscalls from its processes (have 
> I got that right?).

Yep, that is exactly what UML does.

> Anyway, problem solved.

I actually didn't realize the bug in ptrace for awhile.  Sad I went so
long with a broken strace, eh?

I am actually testing a new design for part of the preemption patch that
alleviates the ptrace fix, as the race will no longer exist.

-- 
Robert M. Love
rml at ufl.edu
rml at tech9.net


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