linux-kernel - Re: [PATCH v4 09/29] staging: unisys: visorinput: remove unnecessary locking

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Message-ID: <alpine.DEB.2.11.1606091059590.28031@nanos>
Date:	Thu, 9 Jun 2016 11:01:26 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	David Kershner <david.kershner@...sys.com>
cc:	corbet@....net, mingo@...hat.com, hpa@...or.com,
	gregkh@...uxfoundation.org, erik.arfvidson@...sys.com,
	Tim Sell <timothy.sell@...sys.com>, hofrat@...dl.org,
	dzickus@...hat.com, jes.sorensen@...hat.com,
	alexander.curtin@...sys.com, janani.rvchndrn@...il.com,
	sudipm.mukherjee@...il.com, prarit@...hat.com,
	david.binder@...sys.com, nhorman@...hat.com,
	dan.j.williams@...el.com, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org, driverdev-devel@...uxdriverproject.org,
	sparmaintainer@...sys.com
Subject: Re: [PATCH v4 09/29] staging: unisys: visorinput: remove unnecessary
 locking

On Wed, 8 Jun 2016, David Kershner wrote:
> +	/*
> +	 * If we're not paused, really enable interrupts.
> +	 * Regardless of whether we are paused, set a flag indicating
> +	 * interrupts should be enabled so when we resume, interrupts
> +	 * will really be enabled.
> +	 */
> +	down_write(&devdata->lock_visor_dev);

I think I asked this before, but I might have missed the answer.

Why is this a rw_sempahore? It's never taken with down_read and looking at the
usage sites it's simply a mutex, right?

Thanks,

	tglx