linux-kernel - Re: [PATCH 3/3] fork, vhost: Use CLONE_THREAD to fix freezer/ps regression

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Message-ID: <7b0be276-28ff-1011-8faf-0cba618369a4@oracle.com>
Date:   Sun, 28 May 2023 14:29:50 -0500
From:   Mike Christie <michael.christie@...cle.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Oleg Nesterov <oleg@...hat.com>, linux@...mhuis.info,
        nicolas.dichtel@...nd.com, axboe@...nel.dk,
        torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, mst@...hat.com,
        sgarzare@...hat.com, jasowang@...hat.com, stefanha@...hat.com,
        brauner@...nel.org
Subject: Re: [PATCH 3/3] fork, vhost: Use CLONE_THREAD to fix freezer/ps
 regression

On 5/27/23 8:41 PM, Eric W. Biederman wrote:
> Mike Christie <michael.christie@...cle.com> writes:
> 
>> On 5/23/23 7:15 AM, Oleg Nesterov wrote:
>>>
>>> Now the main question. Whatever we do, SIGKILL/SIGSTOP/etc can come right
>>> before we call work->fn(). Is it "safe" to run this callback with
>>> signal_pending() or fatal_signal_pending() ?
>>
>> The questions before this one I'll leave for the core vhost devs since
>> they know best.
> 
> Let me ask a clarifying question:
> 
> Is it only the call to schedule() in vhost_worker that you are worried
> about not sleeping if signal_pending() or fatal_signal_pending()?

It will only be the vhost_worker call to schedule().

When we do the file_operation's release call, we normally set things up
so the work->fn just fails and cleans up. I can pretty easily move that
code into a helper and do:

if (get_signal(ksig))
	new_function_to_tell_drivers_that_all_work_fns_should_fail()