From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1751255AbcBKUEa (ORCPT <rfc822;w@1wt.eu>);
	Thu, 11 Feb 2016 15:04:30 -0500
Received: from mx1.redhat.com ([209.132.183.28]:34566 "EHLO mx1.redhat.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1751067AbcBKUE3 (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Thu, 11 Feb 2016 15:04:29 -0500
Date: Thu, 11 Feb 2016 21:03:57 +0100
From: Oleg Nesterov <oleg@redhat.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Justin Capella <justincapella@gmail.com>,
        Andrew Lutomirski <luto@kernel.org>, linux-kernel@vger.kernel.org
Subject: Re: rwsem exit_to_usermode
Message-ID: <20160211200356.GA10716@redhat.com>
References: <CAMrEMU-a5UNv7X0QnSPWF6J0hgYH2ON7cVJ7xH2AiKjCuerqUQ@mail.gmail.com> <CALCETrV21Y_ugoX-vTFpnTJyd1_7FSmYB+JOMtEZPuQ7UqUANQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CALCETrV21Y_ugoX-vTFpnTJyd1_7FSmYB+JOMtEZPuQ7UqUANQ@mail.gmail.com>
User-Agent: Mutt/1.5.18 (2008-05-17)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 02/10, Andy Lutomirski wrote:
>
> On Wed, Feb 10, 2016 at 5:05 PM, Justin Capella <justincapella@gmail.com> wrote:
> > http://i.imgur.com/gKamNV3.jpg
> >
> > I encountered this deadlock situation, let me know if there is additional
> > info I can provide, if you're interested...
>
> You're the second person in 24 hours to privately report a bug in that code :-/

Let me add lkml,

> This looks like it's a signal thing, not an entry/exit thing, though.

Looks like someone holds cgroup_threadgroup_rwsem for writing.

Which kernel version? It would be nice to look at sysrq-T output...

Oleg.