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Date:   Wed, 18 Jan 2023 18:35:13 +0000
From:   Matthew Wilcox <willy@infradead.org>
To:     Hillf Danton <hdanton@sina.com>
Cc:     Suren Baghdasaryan <surenb@google.com>, vbabka@suse.cz,
        hannes@cmpxchg.org, mgorman@techsingularity.net,
        peterz@infradead.org, hughd@google.com,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 41/41] mm: replace rw_semaphore with atomic_t in vma_lock
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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@infradead.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.