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Re: [PATCH 11/13] Changes to show virtual ids to user [message #13410 is a reply to message #13344]

Fri, 25 May 2007 15:48

ebiederm
Messages: 1354
Registered: February 2006

Senior Member

Pavel Emelianov <xemul@openvz.org> writes:

> Eric W. Biederman wrote:
>> Pavel Emelianov <xemul@sw.ru> writes:
>>
>>> That's true. Sending of signal from parent ns to children
>>> is tricky question. It has many solutions, I wanted to
>>> discuss which one is better:
>>
>> With unix domain sockets and the like it is conceivable we get
>> a pid transfer from one namespace to another and both namespaces
>> are leaf namespaces. I don't remember we can get a leaf to leaf
>> transfer when sending signals.
>
> We should not allow any transfer from leaf NS to leaf NS.
> Should I explain why?

In a checkpointable context it is a bad thing, and we can prevent it
by carefully setting up all of the namespaces.

However it is a fundamental possibility that exists, and because we
can avoid it with careful setup. I don't see a reason to deny it
if something was either inadvertantly or explicitly causes it
to happen.

Do you have another reason for denying the transfer that I'm
not thinking of?

>>
>> The worst case I can see with pid == 0. Is that it would be a bug
>> that we can fix later. For other cases it would seem to be a user
>> space API thing that we get stuck with for all time.
>
> We cannot trust userspace application to expect some pid other than
> positive. All that we can is either use some always-absent pid or
> send the signal as SI_KERNEL.
>
> Our experience show that making decisions like above causes random
> applications failures that are hard (or even impossible) to debug.

Ok. So I guess I see what you are proposing is picking an arbitrary
pid, say pid == 2, and reserving that in all pid namespaces and using
it when we have a pid that does not map to a specific namespace. I'm
fine with that.

All I care about is that we have a solution, preferably simple,
to the non-mapped pid problem.

Eric

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[Message index]

		[PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Thu, 24 May 2007 12:32
		[PATCH 1/13] Round up the API By: Pavel Emelianov on Thu, 24 May 2007 12:35
		Re: [PATCH 1/13] Round up the API By: serue on Thu, 24 May 2007 16:09
		Re: [PATCH 1/13] Round up the API By: ebiederm on Thu, 24 May 2007 16:22
		Re: [PATCH 1/13] Round up the API By: Pavel Emelianov on Thu, 24 May 2007 16:31
		Re: [PATCH 1/13] Round up the API By: serue on Thu, 24 May 2007 16:48
		Re: [PATCH 1/13] Round up the API By: Pavel Emelianov on Fri, 25 May 2007 07:00
		Re: [PATCH 1/13] Round up the API By: serue on Fri, 25 May 2007 13:02
		[PATCH 2/13] Small preparations for namespaces By: Pavel Emelianov on Thu, 24 May 2007 12:37
		Re: [PATCH 2/13] Small preparations for namespaces By: serue on Thu, 24 May 2007 16:08
		Re: [PATCH 2/13] Small preparations for namespaces By: Pavel Emelianov on Fri, 25 May 2007 06:58
		Re: [PATCH 2/13] Small preparations for namespaces By: serue on Fri, 25 May 2007 13:01
		Re: [PATCH 2/13] Small preparations for namespaces By: Pavel Emelianov on Fri, 25 May 2007 13:21
		Re: [PATCH 2/13] Small preparations for namespaces By: serue on Fri, 25 May 2007 13:55
		[PATCH 3/13] Introduciton of config option and clone flag By: Pavel Emelianov on Thu, 24 May 2007 12:42
		Re: [PATCH 3/13] Introduciton of config option and clone flag By: ebiederm on Thu, 24 May 2007 15:39
		[PATCH 4/13] Introduce the vpid fields and helpers for getting them By: Pavel Emelianov on Thu, 24 May 2007 12:44
		[PATCH 5/13] Expand the pid/task seeking functions set By: Pavel Emelianov on Thu, 24 May 2007 12:46
		Re: [PATCH 5/13] Expand the pid/task seeking functions set By: Dave Hansen on Thu, 24 May 2007 17:11
		Re: [PATCH 5/13] Expand the pid/task seeking functions set By: Pavel Emelianov on Fri, 25 May 2007 07:08
		Re: [PATCH 5/13] Expand the pid/task seeking functions set By: Sukadev Bhattiprolu on Fri, 25 May 2007 23:36
		[PATCH 6/13] Pid allocation/freeing procedures By: Pavel Emelianov on Thu, 24 May 2007 12:49
		[PATCH 7/13] Set virtual pids for a newly cloned task By: Pavel Emelianov on Thu, 24 May 2007 12:53
		[PATCH 8/13] The namespace cloning By: Pavel Emelianov on Thu, 24 May 2007 12:57
		[PATCH 9/13] Make proc be able to have multiple super blocks By: Pavel Emelianov on Thu, 24 May 2007 13:01
		[PATCH 10/13] Make proc draw pids from appropriate namespace By: Pavel Emelianov on Thu, 24 May 2007 13:04
		[PATCH 11/13] Changes to show virtual ids to user By: Pavel Emelianov on Thu, 24 May 2007 13:06
		Re: [PATCH 11/13] Changes to show virtual ids to user By: ebiederm on Thu, 24 May 2007 16:05
		Re: [PATCH 11/13] Changes to show virtual ids to user By: xemul on Thu, 24 May 2007 16:15
		Re: [PATCH 11/13] Changes to show virtual ids to user By: ebiederm on Thu, 24 May 2007 16:33
		Re: [PATCH 11/13] Changes to show virtual ids to user By: Pavel Emelianov on Fri, 25 May 2007 06:33
		Re: [PATCH 11/13] Changes to show virtual ids to user By: ebiederm on Fri, 25 May 2007 15:48
		Re: [PATCH 11/13] Changes to show virtual ids to user By: Cedric Le Goater on Tue, 29 May 2007 12:32
		Re: [PATCH 11/13] Changes to show virtual ids to user By: Pavel Emelianov on Thu, 31 May 2007 07:57
		Re: [PATCH 11/13] Changes to show virtual ids to user By: Pavel Emelianov on Thu, 31 May 2007 08:00
		Re: [PATCH 11/13] Changes to show virtual ids to user By: ebiederm on Thu, 31 May 2007 11:26
		Re: [PATCH 11/13] Changes to show virtual ids to user By: Pavel Emelianov on Thu, 31 May 2007 11:46
		Re: [PATCH 11/13] Changes to show virtual ids to user By: ebiederm on Thu, 31 May 2007 13:41
		[PATCH 12/13] Show appropriate pids in proc By: Pavel Emelianov on Thu, 24 May 2007 13:08
		[PATCH 13/13] Make all proc entres accessible in a namespace By: Pavel Emelianov on Thu, 24 May 2007 13:13
		Instructions of how to make testing easy By: Pavel Emelianov on Thu, 24 May 2007 13:19
		Re: Instructions of how to make testing easy By: Pavel Emelianov on Thu, 24 May 2007 16:16
		Re: Instructions of how to make testing easy By: Cedric Le Goater on Thu, 24 May 2007 14:55
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: serue on Thu, 24 May 2007 15:09
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: xemul on Thu, 24 May 2007 16:11
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: serue on Thu, 24 May 2007 16:59
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: ebiederm on Thu, 24 May 2007 18:56
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: serue on Thu, 24 May 2007 19:10
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Fri, 25 May 2007 07:08
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: serue on Fri, 25 May 2007 13:25
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Fri, 25 May 2007 13:53
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: serue on Fri, 25 May 2007 14:25
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Mon, 28 May 2007 07:48
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: ebiederm on Tue, 29 May 2007 04:30
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Tue, 29 May 2007 07:47
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: ebiederm on Tue, 29 May 2007 12:36
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Fri, 25 May 2007 07:06
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: ebiederm on Fri, 25 May 2007 14:55
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: ebiederm on Thu, 24 May 2007 16:00
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: serue on Thu, 24 May 2007 16:20
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Fri, 25 May 2007 06:29
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: serue on Fri, 25 May 2007 13:29
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Thu, 24 May 2007 16:26
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: ebiederm on Thu, 24 May 2007 19:18
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Fri, 25 May 2007 07:15
		Re: Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: dev on Mon, 28 May 2007 11:50
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: ebiederm on Tue, 29 May 2007 13:07
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Daniel Lezcano on Thu, 24 May 2007 16:41
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Fri, 25 May 2007 07:26
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Daniel Lezcano on Fri, 25 May 2007 08:30

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