linux-kernel - Re: [PATCH 3/5] kernel: add support for TIF_NOTIFY

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Date:   Thu, 15 Oct 2020 17:27:08 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
        io-uring@...r.kernel.org, peterz@...radead.org
Subject: Re: [PATCH 3/5] kernel: add support for TIF_NOTIFY_SIGNAL

On 10/15, Thomas Gleixner wrote:
>
> On Thu, Oct 15 2020 at 16:37, Oleg Nesterov wrote:
> > On 10/15, Jens Axboe wrote:
> >> On 10/15/20 8:31 AM, Oleg Nesterov wrote:
> >> > I don't understand why does this version requires CONFIG_GENERIC_ENTRY.
> >> >
> >> > Afaics, it is very easy to change all the non-x86 arches to support
> >> > TIF_NOTIFY_SIGNAL, but it is not trivial to change them all to use
> >> > kernel/entry/common.c ?
> >>
> >> I think that Thomas wants to gate TIF_NOTIFY_SIGNAL on conversion to
> >> the generic entry code?
> >
> > Then I think TIF_NOTIFY_SIGNAL will be never fully supported ;)
>
> Yeah, we proliferate crap on that basis forever. _ALL_ architectures
> have the very same entry/exit ordering problems (or subsets and
> different ones) which we fixed on x86.
>
> So no, we don't want to have 24 different variants of the same thing
> again. That's what common code is for.
>
> Not doing that is making the life of everyone working on core
> infrastructure pointlessly harder. Architecture people still have enough
> ways to screw everyone up.

Sure, it would be nice to change them all to use kernel/entry/common.c.

Until then (until never), how can we kill JOBCTL_TASK_WORK ?

How can we remove freezing/klp_patch_pending from recalc_sigpending() ?

Oleg.