linux-kernel - Re: [PATCH 41/41] mm: replace rw_semaphore with atomic_t in vma

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <Y8g74YJVonMHpWw/@casper.infradead.org>
Date:   Wed, 18 Jan 2023 18:35:13 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Hillf Danton <hdanton@...a.com>
Cc:     Suren Baghdasaryan <surenb@...gle.com>, vbabka@...e.cz,
        hannes@...xchg.org, mgorman@...hsingularity.net,
        peterz@...radead.org, hughd@...gle.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 41/41] mm: replace rw_semaphore with atomic_t in vma_lock

On Wed, Jan 18, 2023 at 02:26:39PM +0800, Hillf Danton wrote:
> On Tue, Jan 17, 2023 at 10:27 AM Matthew Wilcox <willy@...radead.org> wrote:
> >
> > The cpu_relax() is exactly the wrong thing to do here.  See this thread:
> > https://lore.kernel.org/linux-fsdevel/20230113184447.1707316-1-mjguzik@gmail.com/
> 
> If you are right, feel free to go and remove every cpu_relax() under the
> kernel/locking directory.

I see you didn't read the whole thread where Linus points out that a
cmpxchg() loop is fundamentally different from a spinlock.