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

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Message-ID: <7af78e02-2c4a-ba62-38c0-e927dc5267b7@kernel.dk>
Date:   Thu, 8 Oct 2020 09:00:52 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     linux-kernel@...r.kernel.org, io-uring@...r.kernel.org,
        peterz@...radead.org, tglx@...utronix.de
Subject: Re: [PATCHSET RFC v3 0/6] Add support for TIF_NOTIFY_SIGNAL

On 10/8/20 8:56 AM, 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().

Totally agree, which is why I liked your suggestion of turning it into a
tracehook.

I've rebased and collapsed the series with the changes, initial tests
look good here. I'll run it through some more testing and send out a v4.
I really like that it's down to 3 core patches now, instead of 5, and
the last one is just wiring up task_work. The changes you suggested also
means it's a lot easier to wire up new archs, so we could potentially
have full support for TIF_NOTIFY_SIGNAL very quickly and can drop the
JOBCTL etc parts.

I'll work on that next, if we have agreement that v4 is sound. Thanks a
lot for your reviews, Oleg! It might've started out a bit nasty on the
RFC front, but with the current direction, we'll end up deleting a lot
of extra code on top.

-- 
Jens Axboe