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Subject: Re: [PATCH] livepatch: klp_send_signal should treat PF_IO_WORKER like
 PF_KTHREAD
To:     Miroslav Benes <mbenes@suse.cz>, Dong Kai <dongkai11@huawei.com>
Cc:     jpoimboe@redhat.com, jikos@kernel.org, pmladek@suse.com,
        axboe@kernel.dk, live-patching@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20210325014836.40649-1-dongkai11@huawei.com>
 <alpine.LSU.2.21.2103251023320.30447@pobox.suse.cz>
From:   Joe Lawrence <joe.lawrence@redhat.com>
Message-ID: <01cbab2f-da8b-f289-2241-d258406a4b6c@redhat.com>
Date:   Thu, 25 Mar 2021 12:43:06 -0400
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On 3/25/21 5:26 AM, Miroslav Benes wrote:
> On Thu, 25 Mar 2021, Dong Kai wrote:
> 
>> commit 15b2219facad ("kernel: freezer should treat PF_IO_WORKER like
>> PF_KTHREAD for freezing") is to fix the freezeing issue of IO threads
>> by making the freezer not send them fake signals.
>>
>> Here live patching consistency model call klp_send_signals to wake up
>> all tasks by send fake signal to all non-kthread which only check the
>> PF_KTHREAD flag, so it still send signal to io threads which may lead to
>> freezeing issue of io threads.
> 
> I suppose this could happen, but it will also affect the live patching
> transition if the io threads do not react to signals.
> 
> Are you able to reproduce it easily? I mean, is there a testcase I could
> use to take a closer look?
>   

If repro is only hypothetical at this point, perhaps we can artificially 
create it in selftests?  And useful to verify the future change you 
mentioned in your other reply?

-- Joe