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Date:   Fri, 7 Aug 2020 08:22:36 +0800
From:   Guo Ren <>
To:     Peter Zijlstra <>
Cc:     Ren Guo <>,
        Linux Kernel Mailing List <>,,,
        Will Deacon <>
Subject: Re: csky: smp_mb__after_spinlock

Hi Peter,

On Thu, Aug 6, 2020 at 3:53 AM <> wrote:
> Hi,
> While doing an audit of smp_mb__after_spinlock, I found that csky
> defines it, why?
> CSKY only has smp_mb(), it doesn't override __atomic_acquire_fence or
> otherwise special cases it's atomic*_acquire() primitives. It has an
> explicit smp_mb() in its arch_spin_lock().

Yes, csky didn't implement ACQUIRE/RELEASE in spinlock.h. So it is a
redundant and side-effect wrong macro, we should remove it to fixup.

 - implement csky's ACQUIRE/RELEASE barrier

> Also, why have two implementations of all the locking?

I just kept my baby's codes :P. Now, we could remove it and just keep
the ticket's one.

BTW, I want to change the spinlock to qspinlock, but csky only has
32-bit atomic operation in hardware.

Any plan to deal with this in spinlock?

Maybe for the embedded scenario, qspinlock seems a bit heavy, are any
tickets-like comm spinlock infrastructures in the plan?

Best Regards
 Guo Ren


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