linux-kernel - Re: [PATCHSET RFC v3 0/6] Add support for TIF_NOTIFY

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Message-ID: <e33ec671-3143-d720-176b-a8815996fd1c@kernel.dk>
Date:   Fri, 9 Oct 2020 09:21:25 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Miroslav Benes <mbenes@...e.cz>, Oleg Nesterov <oleg@...hat.com>
Cc:     linux-kernel@...r.kernel.org, io-uring@...r.kernel.org,
        peterz@...radead.org, tglx@...utronix.de,
        live-patching@...r.kernel.org
Subject: Re: [PATCHSET RFC v3 0/6] Add support for TIF_NOTIFY_SIGNAL

On 10/9/20 2:01 AM, Miroslav Benes wrote:
> On Thu, 8 Oct 2020, Oleg Nesterov wrote:
> 
>> On 10/05, Jens Axboe wrote:
>>>
>>> Hi,
>>>
>>> The goal is this patch series is to decouple TWA_SIGNAL based task_work
>>> from real signals and signal delivery.
>>
>> I think TIF_NOTIFY_SIGNAL can have more users. Say, we can move
>> try_to_freeze() from get_signal() to tracehook_notify_signal(), kill
>> fake_signal_wake_up(), and remove freezing() from recalc_sigpending().
>>
>> Probably the same for TIF_PATCH_PENDING, klp_send_signals() can use
>> set_notify_signal() rather than signal_wake_up().
> 
> Yes, that was my impression from the patch set too, when I accidentally 
> noticed it.
> 
> Jens, could you CC our live patching ML when you submit v4, please? It 
> would be a nice cleanup.

Definitely, though it'd be v5 at this point. But we really need to get
all archs supporting TIF_NOTIFY_SIGNAL first. Once we have that, there's
a whole slew of cleanups that'll fall out naturally:

- Removal of JOBCTL_TASK_WORK
- Removal of special path for TWA_SIGNAL in task_work
- TIF_PATCH_PENDING can be converted and then removed
- try_to_freeze() cleanup that Oleg mentioned

And probably more I'm not thinking of right now :-)

-- 
Jens Axboe