To: Hubertus Franke <frankeh@watson.ibm.com>
Cc: Dave Hansen <haveblue@us.ibm.com>, Greg KH <greg@kroah.com>,
       Alan Cox <alan@lxorguk.ukuu.org.uk>,
       "Serge E. Hallyn" <serue@us.ibm.com>,
       Arjan van de Ven <arjan@infradead.org>, linux-kernel@vger.kernel.org,
       Cedric Le Goater <clg@fr.ibm.com>
Subject: Re: RFC [patch 13/34] PID Virtualization Define new task_pid api
References: <20060117143258.150807000@sergelap>
	<20060117143326.283450000@sergelap>
	<1137511972.3005.33.camel@laptopd505.fenrus.org>
	<20060117155600.GF20632@sergelap.austin.ibm.com>
	<1137513818.14135.23.camel@localhost.localdomain>
	<1137518714.5526.8.camel@localhost.localdomain>
	<20060118045518.GB7292@kroah.com>
	<1137601395.7850.9.camel@localhost.localdomain>
	<m1fyniomw2.fsf@ebiederm.dsl.xmission.com>
	<43D14578.6060801@watson.ibm.com>
	<m1hd7xmylo.fsf@ebiederm.dsl.xmission.com>
	<43D52592.8080709@watson.ibm.com>
From: ebiederm@xmission.com (Eric W. Biederman)
Date: Mon, 23 Jan 2006 12:28:14 -0700
In-Reply-To: <43D52592.8080709@watson.ibm.com> (Hubertus Franke's message of
 "Mon, 23 Jan 2006 13:50:58 -0500")
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Hubertus Franke <frankeh@watson.ibm.com> writes:

> Eric W. Biederman wrote:
>> Hubertus Franke <frankeh@watson.ibm.com> writes:
>> Any place the kernel saves a pid and then proceeds to signal it later.
>> At that later point in time it is possibly you will be in the wrong
>> context.
>>
>
> Yes, that's possible.. In the current patch that is not a problem, because
> the internal pid (aka kpid) == <vpid,containerid>  mangeled together.
> So in those cases, the kernel would have to keep <pid, container_id>

Agreed, and for the internal implementation I think having them mangled
together make sense, so long as we never export that form to userspace.

>> This probably justifies having a kpid_t that has both the process
>> space id and the pid in it.  For when the kernel is storing pids to
>> use as weak references, for signal purposes etc.
>>
>
> An that's what the current patch does. Only thing is we did not rename
> everything to kpid_t!

Yep. But because of that you couldn't detect mixing of pid and kpid.

>> At least tty_io.c and fcntl.c have examples where you the caller
>> may not have the proper context.
>
> Can you point those out directly .. thanks..

Short version.  tty's send signals on hangup and f_setown can trigger signals
being sent.

Eric


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