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Re: [patch] PID namespace design bug, workaround

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From: Ulrich Drepper <drepper@...>
To: Pavel Emelyanov <xemul@...>
Cc: Andrew Morton <akpm@...>, Ingo Molnar <mingo@...>, Linus Torvalds <torvalds@...>, <linux-kernel@...>, Sukadev Bhattiprolu <sukadev@...>, Serge Hallyn <serue@...>
Subject: Re: [patch] PID namespace design bug, workaround
Date: Friday, November 2, 2007 - 11:34 am

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Pavel Emelyanov wrote:

No, it's not.  If you'd read the mail carefully you'd notice that the
use of PIDs especially in robust futexes is part of the API and that it
simply isn't acceptable to say "don't do that".  A robust mutex can be
stored in any file and as long as two processes have access to the same
file (or they can pass each other shared memory) the underlying futex
functionality simply must work.

This whole approach to allow switching on and off each of the namespaces
is just wrong.  Do it all or nothing, at least for the problematic ones
like NEWPID.  Having access to the same filesystem but using separate
PID namespaces is simply not going to work.

You also brush completely over the SysV IPC issue.

And I doubt that I spent enough time thinking about all this to arrive
at the more subtle problems.  I don't think especially the PID namespace
is ready at all at this time.

- --
➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖
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Messages in current thread:
[patch] PID namespace design bug, workaround, Ingo Molnar, (Thu Nov 1, 10:43 am)
Re: [patch] PID namespace design bug, workaround, Pavel Emelyanov, (Thu Nov 1, 11:02 am)
Re: [patch] PID namespace design bug, workaround, Ulrich Drepper, (Thu Nov 1, 10:53 am)
Re: [patch] PID namespace design bug, workaround, Ingo Molnar, (Thu Nov 1, 11:05 am)
Re: [patch] PID namespace design bug, workaround, Theodore Tso, (Thu Nov 1, 2:57 pm)
Re: [patch] PID namespace design bug, workaround, Ingo Molnar, (Thu Nov 1, 3:53 pm)
Re: [patch] PID namespace design bug, workaround, Ulrich Drepper, (Thu Nov 1, 8:23 pm)
Re: [patch] PID namespace design bug, workaround, Pavel Emelyanov, (Thu Nov 1, 10:51 am)
Re: [patch] PID namespace design bug, workaround, Ulrich Drepper, (Thu Nov 1, 10:56 am)
Re: [patch] PID namespace design bug, workaround, Dave Hansen, (Thu Nov 1, 12:12 pm)
Re: [patch] PID namespace design bug, workaround, Pavel Emelyanov, (Thu Nov 1, 11:05 am)
Re: [patch] PID namespace design bug, workaround, Ulrich Drepper, (Thu Nov 1, 8:21 pm)
Re: [patch] PID namespace design bug, workaround, Pavel Emelyanov, (Fri Nov 2, 3:55 am)
Re: [patch] PID namespace design bug, workaround, Andrew Morton, (Fri Nov 2, 4:04 am)
Re: [patch] PID namespace design bug, workaround, Dave Hansen, (Fri Nov 2, 1:30 pm)
Re: [patch] PID namespace design bug, workaround, Linus Torvalds, (Fri Nov 2, 1:39 pm)
Re: [patch] PID namespace design bug, workaround, Ingo Molnar, (Sat Nov 3, 4:12 pm)
Futexes and network filesystems., Er ic W. Biederman, (Tue Nov 20, 6:53 pm)
Re: Futexes and network filesystems., Kyle Moffett, (Wed Nov 21, 2:16 am)
Re: Futexes and network filesystems., Eric W. Biederman, (Wed Nov 21, 2:30 am)
Re: [patch] PID namespace design bug, workaround, Linus Torvalds, (Sat Nov 3, 6:40 pm)
Re: [patch] PID namespaces, Ingo Molnar, (Sun Nov 4, 6:38 am)
Re: [patch] PID namespaces, Denys Vlasenko, (Mon Nov 5, 10:47 am)
Re: [patch] PID namespaces, Dave Hansen, (Sun Nov 4, 4:12 pm)
Re: [patch] PID namespace design bug, workaround, Arjan van de Ven, (Sat Nov 3, 7:55 pm)
Re: [patch] PID namespace design bug, workaround, , (Sat Nov 3, 8:21 pm)
Re: [patch] PID namespace design bug, workaround, Nicholas Miell, (Sat Nov 3, 12:02 am)
Re: [patch] PID namespace design bug, workaround, Pavel Emelyanov, (Fri Nov 2, 4:14 am)
Re: [patch] PID namespace design bug, workaround, Ulrich Drepper, (Fri Nov 2, 10:05 am)
Re: [patch] PID namespace design bug, workaround, Pavel Emelyanov, (Fri Nov 2, 10:21 am)
Re: [patch] PID namespace design bug, workaround, , (Sat Nov 3, 4:01 pm)
Re: [patch] PID namespace design bug, workaround, Eric W. Biederman, (Sun Nov 4, 3:17 am)
Re: [patch] PID namespace design bug, workaround, Ulrich Drepper, (Fri Nov 2, 11:34 am)
Re: [patch] PID namespace design bug, workaround, Pavel Emelyanov, (Fri Nov 2, 11:58 am)
Re: [patch] PID namespace design bug, workaround, Ulrich Drepper, (Sat Nov 3, 12:34 am)
Re: [patch] PID namespace design bug, workaround, Pavel Emelyanov, (Tue Nov 6, 3:49 am)
Re: [patch] PID namespace design bug, workaround, Theodore Tso, (Fri Nov 2, 5:39 pm)
Re: [patch] PID namespace design bug, workaround, Peter Zijlstra, (Thu Nov 1, 10:56 am)
Re: [patch] PID namespace design bug, workaround, Pavel Emelyanov, (Thu Nov 1, 11:06 am)
Re: [patch] PID namespace design bug, workaround, Ingo Molnar, (Thu Nov 1, 11:17 am)
Re: [patch] PID namespace design bug, workaround, Pavel Emelyanov, (Thu Nov 1, 11:30 am)