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From:   Shuah Khan <shuahkhan@gmail.com>
Date:   Tue, 3 Oct 2017 15:09:53 -0600
Message-ID: <CAKocOOM6M5HbTA24wStNFnOTVR6vHc76h6cXT=OcMV2e3XSy9w@mail.gmail.com>
Subject: Re: [RFC 5/5] pm: remove kernel thread freezing
To:     Jiri Kosina <jikos@kernel.org>, mchehab@s-opensource.com
Cc:     Pavel Machek <pavel@ucw.cz>,
        "Luis R. Rodriguez" <mcgrof@kernel.org>, viro@zeniv.linux.org.uk,
        bart.vanassche@wdc.com, ming.lei@redhat.com, tytso@mit.edu,
        darrick.wong@oracle.com, rjw@rjwysocki.net, len.brown@intel.com,
        linux-fsdevel@vger.kernel.org, boris.ostrovsky@oracle.com,
        jgross@suse.com, todd.e.brandt@linux.intel.com, nborisov@suse.com,
        jack@suse.cz, martin.petersen@oracle.com, ONeukum@suse.com,
        oleksandr@natalenko.name, oleg.b.antonyan@gmail.com,
        Linux PM list <linux-pm@vger.kernel.org>,
        linux-block@vger.kernel.org, linux-xfs@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>, linux-media@vger.kernel.org,
        shuahkh@osg.samsung.com
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On Tue, Oct 3, 2017 at 3:00 PM, Jiri Kosina <jikos@kernel.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

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