linux-kernel - Re: [PATCH v2 2/2] exit: pidns: fix/update the comments in zap_pid_ns

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Message-ID: <20141201232442.GA10487@redhat.com>
Date:	Tue, 2 Dec 2014 00:24:42 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Aaron Tomlin <atomlin@...hat.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	Serge Hallyn <serge.hallyn@...ntu.com>,
	Sterling Alexander <stalexan@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] exit: pidns: fix/update the comments in
	zap_pid_ns_processes()

On 12/01, Andrew Morton wrote:
>
> On Thu, 27 Nov 2014 00:54:37 +0100 Oleg Nesterov <oleg@...hat.com> wrote:
>
> > The comments in zap_pid_ns_processes() are not clear, we need to
> > explain how this code actually works.
>
> Could we please get some documentation for PIDNS_HASH_ADDING?  What it
> does, what is the protocol for handling it, etc?  I was trying to
> review your [1/2] but this little mystery has me somewhat stumped.

OK, I'll send another simple doc patch.

But in short it is simple. "nr_hashed & PIDNS_HASH_ADDING" just means
that this pid_ns is alive, and alloc_pid() can succeed. We need this to
ensure that a new child can't be injected after zap_pid_ns_processes()
has already killed all tasks in its pid_ns.

Oleg.

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