linux-kernel - Re: [PATCH v7 1/5] locking/qspinlock: Rename mcs lock/unlock macros and make them more generic

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Message-ID: <20200122091547.GU14879@hirez.programming.kicks-ass.net>
Date:   Wed, 22 Jan 2020 10:15:47 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Alex Kogan <alex.kogan@...cle.com>
Cc:     linux@...linux.org.uk, 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,
        guohanjun@...wei.com, jglauber@...vell.com,
        steven.sistare@...cle.com, daniel.m.jordan@...cle.com,
        dave.dice@...cle.com, rahul.x.yadav@...cle.com
Subject: Re: [PATCH v7 1/5] locking/qspinlock: Rename mcs lock/unlock macros
 and make them more generic

On Mon, Nov 25, 2019 at 04:07:05PM -0500, Alex Kogan wrote:

> --- a/arch/arm/include/asm/mcs_spinlock.h
> +++ b/arch/arm/include/asm/mcs_spinlock.h
> @@ -6,7 +6,7 @@
>  #include <asm/spinlock.h>
>  
>  /* MCS spin-locking. */
> -#define arch_mcs_spin_lock_contended(lock)				\
> +#define arch_mcs_spin_lock(lock)				\
>  do {									\
>  	/* Ensure prior stores are observed before we enter wfe. */	\
>  	smp_mb();							\
> @@ -14,9 +14,9 @@ do {									\
>  		wfe();							\
>  } while (0)								\
>  
> -#define arch_mcs_spin_unlock_contended(lock)				\
> +#define arch_mcs_pass_lock(lock, val)					\
>  do {									\
> -	smp_store_release(lock, 1);					\
> +	smp_store_release((lock), (val));				\
>  	dsb_sev();							\
>  } while (0)

So I hate those names; it used to be clear this was the contended path,
not so anymore. arch_mcs_spin_lock() in particular is grossly misnamed
now.

's/arch_mcs_spin_lock/arch_mcs_spin_wait/g' could perhaps work, if you
really want to get rid of the _contended suffix.

Also, pass_lock seems unfortunately named...