linux-kernel - Re: [RFC 5/5] pm: remove kernel thread freezing

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Date:   Tue, 3 Oct 2017 20:21:42 +0000
From:   Bart Van Assche <Bart.VanAssche@....com>
To:     "jikos@...nel.org" <jikos@...nel.org>
CC:     "boris.ostrovsky@...cle.com" <boris.ostrovsky@...cle.com>,
        "ONeukum@...e.com" <ONeukum@...e.com>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "nborisov@...e.com" <nborisov@...e.com>,
        "oleg.b.antonyan@...il.com" <oleg.b.antonyan@...il.com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>,
        "pavel@....cz" <pavel@....cz>,
        "darrick.wong@...cle.com" <darrick.wong@...cle.com>,
        "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
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        "len.brown@...el.com" <len.brown@...el.com>,
        "tytso@....edu" <tytso@....edu>, "jack@...e.cz" <jack@...e.cz>
Subject: Re: [RFC 5/5] pm: remove kernel thread freezing

On Tue, 2017-10-03 at 22:17 +0200, Jiri Kosina wrote:
> On Tue, 3 Oct 2017, Bart Van Assche wrote:
> > What about the many drivers outside filesystems that use the 
> > set_freezable() / try_to_freeze() / wait_event_freezable() API?
> 
> Many/most of them are just completely bogus and pointless. I've killed a 
> lot of those in the past, but the copy/paste programming is just too 
> strong enemy to fight against.

If just a single driver would use that API to prevent that I/O occurs while
processes are frozen then this patch will break that driver. I would like to
know your opinion about the following patch in particular: "[PATCH v4 1/7] md:
Make md resync and reshape threads freezable"
(https://www.spinics.net/lists/linux-block/msg17854.html).

Thanks,

Bart.