linux-kernel - Re: [PATCH 1/3] picolcd: driver for PicoLCD HID device

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Message-ID: <20100226081514.GB17444@core.coreip.homeip.net>
Date:	Fri, 26 Feb 2010 00:15:15 -0800
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	Bruno Prémont <bonbons@...ux-vserver.org>,
	linux-input@...r.kernel.org, linux-usb@...r.kernel.org,
	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Rick L. Vinyard Jr." <rvinyard@...nmsu.edu>,
	Nicu Pavel <npavel@...ner.com>
Subject: Re: [PATCH 1/3] picolcd: driver for PicoLCD HID device

On Thu, Feb 25, 2010 at 12:07:38PM +0100, Jiri Kosina wrote:
> On Wed, 24 Feb 2010, Bruno Prémont wrote:
> 
> > +/* Update fb_vbitmap from the screen_base and send changed tiles to device */
> > +static void picolcd_fb_update(struct picolcd_data *data)
> > +{
> > +	int chip, tile;
> > +
> > +	spin_lock(&data->lock);
> > +	if (!(data->status & PICOLCD_READY_FB)) {
> > +		spin_unlock(&data->lock);
> > +		picolcd_fb_reset(data->hdev, 0);
> > +	} else
> > +		spin_unlock(&data->lock);
> 
> Please put the brackets to the else branch as well.
> 
Well, it looks like it can be rewritten as:

	spin_lock(&data->lock);
	need_reset = !(data->status & PICOLCD_READY_FB);
	spin_unlock(&data->lock);

	if (need_reset)
		picolcd_fb_reset(data->hdev, 0);

Which plainly shows that the locking here is bogus.

-- 
Dmitry
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