linux-kernel - Re: [PATCH] livepatch: klp_send_signal should treat PF_IO_WORKER like PF

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Message-ID: <01cbab2f-da8b-f289-2241-d258406a4b6c@redhat.com>
Date:   Thu, 25 Mar 2021 12:43:06 -0400
From:   Joe Lawrence <joe.lawrence@...hat.com>
To:     Miroslav Benes <mbenes@...e.cz>, Dong Kai <dongkai11@...wei.com>
Cc:     jpoimboe@...hat.com, jikos@...nel.org, pmladek@...e.com,
        axboe@...nel.dk, live-patching@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] livepatch: klp_send_signal should treat PF_IO_WORKER like
 PF_KTHREAD

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