Re: [PATCH 41/41] mm: replace rw_semaphore with atomic_t in vma_lock

[Matthew Wilcox]

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@xxxxxxxxxxxxx> 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@xxxxxxxxx/
> 
> 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.