linux-kernel - Re: [PATCH v7 4/4] qrwlock: Use smp_store_release() in write

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Message-ID: <20131217192439.GD15969@linux.vnet.ibm.com>
Date:	Tue, 17 Dec 2013 11:24:39 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Waiman Long <Waiman.Long@...com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Arnd Bergmann <arnd@...db.de>,
	linux-arch@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michel Lespinasse <walken@...gle.com>,
	Andi Kleen <andi@...stfloor.org>,
	Rik van Riel <riel@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	George Spelvin <linux@...izon.com>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	"Aswin Chandramouleeswaran\"" <aswin@...com>,
	Scott J Norton <scott.norton@...com>
Subject: Re: [PATCH v7 4/4] qrwlock: Use smp_store_release() in write_unlock()

On Fri, Nov 22, 2013 at 02:04:47PM -0500, Waiman Long wrote:
> This patch modifies the queue_write_unlock() function to use the
> new smp_store_release() function in another pending patch. This patch
> should only be merged if the other patch was merged.
> 
> Signed-off-by: Waiman Long <Waiman.Long@...com>

Reviewed-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

> ---
>  include/asm-generic/qrwlock.h |    4 +---
>  1 files changed, 1 insertions(+), 3 deletions(-)
> 
> diff --git a/include/asm-generic/qrwlock.h b/include/asm-generic/qrwlock.h
> index 335473a..59c5972 100644
> --- a/include/asm-generic/qrwlock.h
> +++ b/include/asm-generic/qrwlock.h
> @@ -176,9 +176,7 @@ static inline void queue_write_unlock(struct qrwlock *lock)
>  	/*
>  	 * Make sure that none of the critical section will be leaked out.
>  	 */
> -	smp_mb__before_clear_bit();
> -	ACCESS_ONCE(lock->cnts.writer) = 0;
> -	smp_mb__after_clear_bit();
> +	smp_store_release(&lock->cnts.writer, 0)
>  }
> 
>  /*
> -- 
> 1.7.1
> 

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