linux-kernel - Re: [PATCH v2] arch/powerpc/include/asm/barrier.h: redefine rmb and wmb to lwsync

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Date:   Wed, 22 Feb 2023 09:51:22 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Kautuk Consul <kconsul@...ux.vnet.ibm.com>
CC:     Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Rohan McLure <rmclure@...ux.ibm.com>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] arch/powerpc/include/asm/barrier.h: redefine rmb and
 wmb to lwsync



Le 22/02/2023 à 10:46, Kautuk Consul a écrit :
>>
>> Reviewed-by: Christophe Leroy <christophe.leroy@...roup.eu>
> Thanks!
>>
>>> ---
>>>    arch/powerpc/include/asm/barrier.h | 7 +++++++
>>>    1 file changed, 7 insertions(+)
>>>
>>> diff --git a/arch/powerpc/include/asm/barrier.h b/arch/powerpc/include/asm/barrier.h
>>> index b95b666f0374..e088dacc0ee8 100644
>>> --- a/arch/powerpc/include/asm/barrier.h
>>> +++ b/arch/powerpc/include/asm/barrier.h
>>> @@ -36,8 +36,15 @@
>>>     * heavy-weight sync, so smp_wmb() can be a lighter-weight eieio.
>>>     */
>>>    #define __mb()   __asm__ __volatile__ ("sync" : : : "memory")
>>> +
>>> +/* The sub-arch has lwsync. */
>>> +#if defined(CONFIG_PPC64) || defined(CONFIG_PPC_E500MC)
>>> +#define __rmb() __asm__ __volatile__ ("lwsync" : : : "memory")
>>> +#define __wmb() __asm__ __volatile__ ("lwsync" : : : "memory")
>>
>> I'd have preferred with 'asm volatile' though.
> Sorry about that! That wasn't the intent of this patch.
> Probably another patch series should change this manner of #defining
> assembly.

Why adding new line wrong then have to have another patch to make them 
right ?

When you build a new house in an old village, you first build your house 
with old materials and then you replace everything with new material ?