linux-kernel - Re: [PATCH 14/33] locking/atomic: arc: move to ARCH

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Date:   Mon, 10 May 2021 19:48:58 +0000
From:   Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:     Mark Rutland <mark.rutland@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "will@...nel.org" <will@...nel.org>,
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Subject: Re: [PATCH 14/33] locking/atomic: arc: move to ARCH_ATOMIC

On 5/10/21 7:57 AM, Mark Rutland wrote:
> On Mon, May 10, 2021 at 10:37:34AM +0100, Mark Rutland wrote:
>> We'd like all architectures to convert to ARCH_ATOMIC, as once all
>> architectures are converted it will be possible to make significant
>> cleanups to the atomics headers, and this will make it much easier to
>> generically enable atomic functionality (e.g. debug logic in the
>> instrumented wrappers).
>>
>> As a step towards that, this patch migrates arc to ARCH_ATOMIC. The arch
>> code provides arch_{atomic,atomic64,xchg,cmpxchg}*(), and common code
>> wraps these with optional instrumentation to provide the regular
>> functions.
>>
>> Signed-off-by: Mark Rutland <mark.rutland@....com>
>> Cc: Boqun Feng <boqun.feng@...il.com>
>> Cc: Peter Zijlstra <peterz@...radead.org>
>> Cc: Vineet Gupta <vgupta@...opsys.com>
>> Cc: Will Deacon <will@...nel.org>

Acked-by: Vineet Gupta <vgupta@...opsys,com>    #arch/arc

FWIW, I do have a bunch of ARC specific cleanups and updates for 
atomics/bitops/cmpxchg from my arc64 work, which I'm planning to send 
out soon. That will be independent of this changeset for now, but we'll 
have this one merge first.

Thx for doing this.
-Vineet

>> ---
>>   arch/arc/Kconfig               |  1 +
>>   arch/arc/include/asm/atomic.h  | 56 +++++++++++++++++++++---------------------
>>   arch/arc/include/asm/cmpxchg.h |  8 +++---
>>   3 files changed, 33 insertions(+), 32 deletions(-)
> I evidently missed atomic_xchg() in asm/cmpxchg.h, so the fixup below is
> needed. I've pushed that to my branch on kernel.org for now.
>
> Mark.
>
> ---->8----
> diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h
> index 87666980b78a..d1781bdf6527 100644
> --- a/arch/arc/include/asm/cmpxchg.h
> +++ b/arch/arc/include/asm/cmpxchg.h
> @@ -153,6 +153,6 @@ static inline unsigned long __xchg(unsigned long val, volatile void *ptr,
>    *         can't be clobbered by others. Thus no serialization required when
>    *         atomic_xchg is involved.
>    */
> -#define atomic_xchg(v, new) (xchg(&((v)->counter), new))
> +#define arch_atomic_xchg(v, new) (arch_xchg(&((v)->counter), new))
>   
>   #endif