From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Luis R. Rodriguez" <mcgrof@kernel.org>
Subject: Re: [Regression/XFS/PM] Freeze tasks failed in xfsaild
Date: Mon, 13 Nov 2017 21:14:14 +0100
Message-ID: <20171113201414.GD16026@wotan.suse.de>
References: <20171113103139.GA18936@yu-chen.sh.intel.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Return-path: <linux-pm-owner@vger.kernel.org>
Received: from mx2.suse.de ([195.135.220.15]:39661 "EHLO mx2.suse.de"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1753414AbdKMUOR (ORCPT <rfc822;linux-pm@vger.kernel.org>);
        Mon, 13 Nov 2017 15:14:17 -0500
Content-Disposition: inline
In-Reply-To: <20171113103139.GA18936@yu-chen.sh.intel.com>
Sender: linux-pm-owner@vger.kernel.org
List-Id: linux-pm@vger.kernel.org
To: Yu Chen <yu.c.chen@intel.com>
Cc: Michal Hocko <mhocko@suse.com>, Hendrik Woltersdorf <hendrikw@arcor.de>, Dave Chinner <dchinner@redhat.com>, "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>, "Darrick J. Wong" <darrick.wong@oracle.com>, Jiri Kosina <jkosina@suse.cz>, Len Brown <len.brown@intel.com>, Rui Zhang <rui.zhang@intel.com>, Dan Williams <dan.j.williams@intel.com>, Yu Chen <yu.chen.surf@gmail.com>, linux-xfs@vger.kernel.org, linux-pm@vger.kernel.org, inux-kernel@vger.kernel.org

On Mon, Nov 13, 2017 at 06:31:39PM +0800, Yu Chen wrote:
> The xfs-buf/dm-1 should be freezed according to
> commit 8018ec083c72 ("xfs: mark all internal workqueues
> as freezable"), thus a easier way might be have to revert
> commit 18f1df4e00ce ("xfs: Make xfsaild freezeable
> again") for now, after this reverting the xfsaild/dm-1
> becomes non-freezable again, thus pm does not see this
> thread - unless we find a graceful way to treat xfsaild/dm-1
> as 'frozen' if it is waiting for an already 'frozen' task,
> or if the filesystem freeze is added in.
> 
> Any comments would be much appreciated.

Reverting 18f1df4e00ce ("xfs: Make xfsaild freezeable again")
would break the proper form of the kthread for it to be freezable.
This "form" is not defined formally, and sadly its just a form
learned throughout years over different kthreads in the kernel.

I'm also not convinced all our hibernation / suspend woes would be fixed by
reverting this commit, its why I worked instead on formalizing a proper freeze
/ thaw, which a lot of filesystems already implement prior to system
hibernation / suspend / resume [0].

I'll be respinning this series without the last patch, provided I'm able to
ensure I don't need the ext[234] hack I did in that thread. Can you test the
first 3 patches *only* on that series and seeing if that helps on your XFS
front as well?

[0] https://lkml.kernel.org/r/20171003185313.1017-1-mcgrof@kernel.org

  Luis