linux-kernel - Re: [PATCH] task_work: Consume only item at a time while invoking the callbacks.

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Message-ID: <20250226142914.GF8995@redhat.com>
Date: Wed, 26 Feb 2025 15:29:15 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: linux-kernel@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
	Frederic Weisbecker <frederic@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Waiman Long <longman@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] task_work: Consume only item at a time while invoking
 the callbacks.

On 02/26, Sebastian Andrzej Siewior wrote:
>
> On 2025-02-23 23:40:15 [+0100], Oleg Nesterov wrote:
> > Well... I won't really argue because I can't suggest a better fix at
> > least right now. Most probably never.
> >
> > However, let me say that this patch doesn't make me happy ;) See below.
> >
> > On 02/21, Sebastian Andrzej Siewior wrote:
> > >
> > > Oleg pointed out that this might be problematic if one closes 2.000.000
> > > files at once. While testing this scenario by opening that many files
> > > following by exit() to ensure that all files are closed at once, I did
> > > not observe anything outside of noise.
> >
> > and this probably means that we can revert c82199061009 ("task_work: remove
> > fifo ordering guarantee") and restore the fifo ordering which IMO makes much
> > more sense.
>
> So assume that turning around will fix the problem because the cancel
> callback is run first followed by the clean up.

Not really, they can run in any order, so fifo can't really help.

But this doesn't matter, please see another email:
https://lore.kernel.org/all/20250226125048.GC8995@redhat.com/

Oleg.