linux-kernel - Re: [PATCH v3 2/2] pid: only take pidmap

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Message-ID: <CAGudoHFjrMsQaDzndo3sM1Jn_WROBrZ0PeQbU89-tDakLAOvew@mail.gmail.com>
Date: Sun, 7 Dec 2025 10:21:35 +0100
From: Mateusz Guzik <mjguzik@...il.com>
To: Matthew Wilcox <willy@...radead.org>
Cc: oleg@...hat.com, brauner@...nel.org, linux-kernel@...r.kernel.org, 
	akpm@...ux-foundation.org, linux-mm@...ck.org
Subject: Re: [PATCH v3 2/2] pid: only take pidmap_lock once on alloc

On Sun, Dec 7, 2025 at 8:21 AM Matthew Wilcox <willy@...radead.org> wrote:
>
> On Sat, Dec 06, 2025 at 02:19:55PM +0100, Mateusz Guzik wrote:
> > -     if (!pid)
> > +     if (unlikely(!pid))
>
> Does this change anything?  I was under the impression that gcc already
> treats !p as unlikely.

I don't know if gcc is guaranteed to act like that, most of my
experience is with clang which was rather inconsistent about it.