Message-ID: <1496318134.2790.18.camel@codethink.co.uk>
Subject: Re: [PATCH 4.4 040/103] pid_ns: Sleep in TASK_INTERRUPTIBLE in
 zap_pid_ns_processes
From: Ben Hutchings <ben.hutchings@codethink.co.uk>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org,
        Vovo Yang <vovoy@google.com>, Guenter Roeck <linux@roeck-us.net>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Thu, 01 Jun 2017 12:55:34 +0100
In-Reply-To: <20170523200900.480278614@linuxfoundation.org>
References: <20170523200856.903752266@linuxfoundation.org>
         <20170523200900.480278614@linuxfoundation.org>
Organization: Codethink Ltd.
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On Tue, 2017-05-23 at 22:09 +0200, Greg Kroah-Hartman wrote:
> 4.4-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Eric W. Biederman <ebiederm@xmission.com>
> 
> commit b9a985db98961ae1ba0be169f19df1c567e4ffe0 upstream.
> 
> The code can potentially sleep for an indefinite amount of time in
> zap_pid_ns_processes triggering the hung task timeout, and increasing
> the system average.  This is undesirable.  Sleep with a task state of
> TASK_INTERRUPTIBLE instead of TASK_UNINTERRUPTIBLE to remove these
> undesirable side effects.
[...]

This seems to rely on the task not actually being signallable due to the
PF_EXITING flag.  Using TASK_IDLE would be clearer (though less
backport-able).

Ben.

-- 
Ben Hutchings
Software Developer, Codethink Ltd.