linux-kernel - Re: [GIT PULL] scheduler changes for v6.4

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Message-ID: <ZEzBPiOp+QylKD4A@gmail.com>
Date:   Sat, 29 Apr 2023 09:03:26 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>
Subject: Re: [GIT PULL] scheduler changes for v6.4


* Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:

> On 2023-04-28 18:02, Linus Torvalds wrote:
> > On Thu, Apr 27, 2023 at 1:51 PM Ingo Molnar <mingo@...nel.org> wrote:
> > > 
> > >   - Fix performance regression introduced by mm_cid
> > 
> > This causes a conflict with commit b20b0368c614 ("mm: fix memory leak
> > on mm_init error handling") that came in through the MM tree.
> > 
> > That conflict is trivial to resolve, and I did so.
> > 
> > Except I also checked my resolution with what was going on in
> > linux-next, and it's different.
> > 
> > I'm pretty sure the resolution in linux-next is wrong, but I thought
> > I'd mention this, since clearly this wasn't caught in linux-next.
> > 
> > Or maybe it's me that did it wrong, but hey, that couldn't actually
> > happen, could it?
> 
> I've reviewed both merge commits (c79e0731da from next-20230428 and
> 586b222d74 from master) and I confirm that your conflict resolution
> is correct. The one in next was wrong.

Indeed - mm_alloc_cid() happens after the MM context has already been 
initialized, so the fail_cid label needs to deinit the context aka call 
destroy_context().

So the resolution by Linus is the correct one:

        mm_destroy_cid(mm);
 fail_cid:
        destroy_context(mm);
 fail_nocontext:
        mm_free_pgd(mm);

Thanks,

	Ingo