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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAKocOOM6M5HbTA24wStNFnOTVR6vHc76h6cXT=OcMV2e3XSy9w@mail.gmail.com>
Date:   Tue, 3 Oct 2017 15:09:53 -0600
From:   Shuah Khan <shuahkhan@...il.com>
To:     Jiri Kosina <jikos@...nel.org>, mchehab@...pensource.com
Cc:     Pavel Machek <pavel@....cz>,
        "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 list <linux-pm@...r.kernel.org>,
        linux-block@...r.kernel.org, linux-xfs@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>, linux-media@...r.kernel.org,
        shuahkh@....samsung.com
Subject: Re: [RFC 5/5] pm: remove kernel thread freezing

On Tue, Oct 3, 2017 at 3:00 PM, Jiri Kosina <jikos@...nel.org> wrote:
> 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.
>

There are about 36 drivers that call try_to_freeze() and half (18 ) of
those are media drivers. Maybe it is easier handle sub-system by
sub-system basis for a review of which one of these usages could be
removed. cc'ing Mauro and linux-media

thanks,
-- Shuah