linux-kernel - Re: [PATCH v5 05/45] percpu_rwlock: Make percpu-rwlocks IRQ-safe, optimally

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Message-ID: <20130210184209.GA3041@redhat.com>
Date:	Sun, 10 Feb 2013 19:42:09 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc:	tglx@...utronix.de, peterz@...radead.org, tj@...nel.org,
	paulmck@...ux.vnet.ibm.com, rusty@...tcorp.com.au,
	mingo@...nel.org, akpm@...ux-foundation.org, namhyung@...nel.org,
	rostedt@...dmis.org, wangyun@...ux.vnet.ibm.com,
	xiaoguangrong@...ux.vnet.ibm.com, rjw@...k.pl, sbw@....edu,
	fweisbec@...il.com, linux@....linux.org.uk,
	nikunj@...ux.vnet.ibm.com, linux-pm@...r.kernel.org,
	linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linuxppc-dev@...ts.ozlabs.org, netdev@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 05/45] percpu_rwlock: Make percpu-rwlocks IRQ-safe,
	optimally

only one cosmetic nit...

On 01/22, Srivatsa S. Bhat wrote:
>
> +#define READER_PRESENT		(1UL << 16)
> +#define READER_REFCNT_MASK	(READER_PRESENT - 1)
> +
>  #define reader_uses_percpu_refcnt(pcpu_rwlock, cpu)			\
>  		(ACCESS_ONCE(per_cpu(*((pcpu_rwlock)->reader_refcnt), cpu)))
>
>  #define reader_nested_percpu(pcpu_rwlock)				\
> -			(__this_cpu_read(*((pcpu_rwlock)->reader_refcnt)) > 1)
> +	(__this_cpu_read(*((pcpu_rwlock)->reader_refcnt)) & READER_REFCNT_MASK)
>
>  #define writer_active(pcpu_rwlock)					\
>  			(__this_cpu_read(*((pcpu_rwlock)->writer_signal)))

I think this all can go to lib/percpu-rwlock.c. Nobody needs to know
these implementation details.

Oleg.

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