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

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Date:   Thu, 30 Nov 2017 00:05:32 +0100
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     Bart Van Assche <Bart.VanAssche@....com>
Cc:     "rjw@...ysocki.net" <rjw@...ysocki.net>,
        "mcgrof@...nel.org" <mcgrof@...nel.org>,
        "boris.ostrovsky@...cle.com" <boris.ostrovsky@...cle.com>,
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        "oleg.b.antonyan@...il.com" <oleg.b.antonyan@...il.com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
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        "tytso@....edu" <tytso@....edu>, "jack@...e.cz" <jack@...e.cz>
Subject: Re: [RFC 5/5] pm: remove kernel thread freezing

On Wed, Oct 04, 2017 at 01:03:54AM +0000, Bart Van Assche wrote:
> On Wed, 2017-10-04 at 02:47 +0200, Luis R. Rodriguez wrote:
> >   3) Lookup for kthreads which seem to generate IO -- address / review if
> >      removal of the freezer API can be done somehow with a quescing. This
> >      is currently for example being done on SCSI / md.
> >  4) Only after all the above is done should we consider this patch or some
> >     form of it.
> 
> After having given this more thought, I think we should omit these last two
> steps. Modifying the md driver such that it does not submit I/O requests while
> processes are frozen requires either to use the freezer API or to open-code it.
> I think there is general agreement in the kernel community that open-coding a
> single mechanism in multiple drivers is wrong. Does this mean that instead of
> removing the freezer API we should keep it and review all its users instead?

Agreed.

  Luis