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

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Message-ID: <nycvar.YFH.7.76.1710032258540.17517@jbgna.fhfr.qr>
Date:   Tue, 3 Oct 2017 23:00:56 +0200 (CEST)
From:   Jiri Kosina <jikos@...nel.org>
To:     Pavel Machek <pavel@....cz>
cc:     "Luis R. Rodriguez" <mcgrof@...nel.org>, viro@...iv.linux.org.uk,
        bart.vanassche@....com, ming.lei@...hat.com, tytso@....edu,
        darrick.wong@...cle.com, rjw@...ysocki.net, len.brown@...el.com,
        linux-fsdevel@...r.kernel.org, boris.ostrovsky@...cle.com,
        jgross@...e.com, todd.e.brandt@...ux.intel.com, nborisov@...e.com,
        jack@...e.cz, martin.petersen@...cle.com, ONeukum@...e.com,
        oleksandr@...alenko.name, oleg.b.antonyan@...il.com,
        linux-pm@...r.kernel.org, linux-block@...r.kernel.org,
        linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC 5/5] pm: remove kernel thread freezing

On Tue, 3 Oct 2017, Pavel Machek wrote:

> > Again, I agree that the (rare) kthreads that are actually "creating" new 
> > I/O have to be somehow frozen and require special care.
> 
> Agreed. Was any effort made to identify those special kernel threads?

I don't think there is any other way than just inspecting all the 
try_to_freeze() instances in the kernel, and understanding what that 
particular kthread is doing.

I've cleaned up most of the low-hanging fruit already, where the 
try_to_freeze() was obviously completely pointless, but a lot more time 
needs to be invested into this.

-- 
Jiri Kosina
SUSE Labs