linux-kernel - Re: [PATCH] pidfd: prevent creation of pidfds for kthreads

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Message-ID: <20240801135900.GD4038@redhat.com>
Date: Thu, 1 Aug 2024 15:59:01 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Christian Brauner <brauner@...nel.org>
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Aleksa Sarai <cyphar@...har.com>,
	Tycho Andersen <tandersen@...flix.com>,
	Daan De Meyer <daan.j.demeyer@...il.com>, Tejun Heo <tj@...nel.org>,
	stable@...r.kernel.org
Subject: Re: [PATCH] pidfd: prevent creation of pidfds for kthreads

On 08/01, Christian Brauner wrote:
>
> On Thu, Aug 01, 2024 at 10:01:20AM GMT, Oleg Nesterov wrote:
> > OK, I won't argue, but ....
> >
> > > you may or may not get notified
> > > via poll when a kthread exits.
> >
> > Why? the exiting kthread should not differ in this respect?
>
> Why do you want to allow it?

Again, I didn't try to "nack" your patch. Just tried to understand
your motivation.

And "may not get notified" above doesn't look right to me...

> > /proc/$pid/status has a "Kthread" field...
>
> Going forward, I don't want to force people to parse basic stuff out of
> procfs. Ideally, they'll be able to mostly rely on pidfd operations
> only.

Agreed.

Oleg.