linux-kernel - Re: [PATCH v4 1/5] locking/qspinlock: Rename arch_mcs_spin_unlock_contended to arch_mcs_pass

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Date:   Tue, 17 Sep 2019 14:25:45 +0800
From:   Hanjun Guo <guohanjun@...wei.com>
To:     Alex Kogan <alex.kogan@...cle.com>, <linux@...linux.org.uk>,
        <peterz@...radead.org>, <mingo@...hat.com>, <will.deacon@....com>,
        <arnd@...db.de>, <longman@...hat.com>,
        <linux-arch@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <tglx@...utronix.de>,
        <bp@...en8.de>, <hpa@...or.com>, <x86@...nel.org>,
        <jglauber@...vell.com>
CC:     <steven.sistare@...cle.com>, <daniel.m.jordan@...cle.com>,
        <dave.dice@...cle.com>, <rahul.x.yadav@...cle.com>
Subject: Re: [PATCH v4 1/5] locking/qspinlock: Rename
 arch_mcs_spin_unlock_contended to arch_mcs_pass_lock and make it more generic

Hi Alex,

On 2019/9/6 22:25, Alex Kogan wrote:
> The new macro should accept the value to be stored into the lock argument
> as another argument. This allows using the same macro in cases where the
> value to be stored when passing the lock is different from 1.
> 
> Signed-off-by: Alex Kogan <alex.kogan@...cle.com>
> Reviewed-by: Steve Sistare <steven.sistare@...cle.com>
> ---
>  arch/arm/include/asm/mcs_spinlock.h | 4 ++--
>  kernel/locking/mcs_spinlock.h       | 6 +++---
>  kernel/locking/qspinlock.c          | 2 +-
>  3 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm/include/asm/mcs_spinlock.h b/arch/arm/include/asm/mcs_spinlock.h
> index 529d2cf4d06f..f3f9efdcd2ca 100644
> --- a/arch/arm/include/asm/mcs_spinlock.h
> +++ b/arch/arm/include/asm/mcs_spinlock.h
> @@ -14,9 +14,9 @@ do {									\
>  		wfe();							\
>  } while (0)								\
>  
> -#define arch_mcs_spin_unlock_contended(lock)				\
> +#define arch_mcs_pass_lock(lock, val)					\

arch_mcs_spin_unlock_contended() has a matching function arch_mcs_spin_lock_contended(),
please see include/asm-generic/mcs_spinlock.h, so if we update this function name,
should we update the matching one as well? and update the relevant comments as well?

>  do {									\
> -	smp_store_release(lock, 1);					\
> +	smp_store_release((lock), (val));				\
>  	dsb_sev();							\
>  } while (0)
>  
> diff --git a/kernel/locking/mcs_spinlock.h b/kernel/locking/mcs_spinlock.h
> index 5e10153b4d3c..84327ca21650 100644
> --- a/kernel/locking/mcs_spinlock.h
> +++ b/kernel/locking/mcs_spinlock.h
> @@ -41,8 +41,8 @@ do {									\
>   * operations in the critical section has been completed before
>   * unlocking.
>   */
> -#define arch_mcs_spin_unlock_contended(l)				\

Before this line of the code, there is:

#ifndef arch_mcs_spin_lock_contended

...

#define arch_mcs_spin_lock_contended(l)                 \

So #ifndef should be updated too.

Thanks
Hanjun