linux-kernel - Re: [PATCH] fbmem: fix copy_from/to

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Date:	Mon, 19 Jan 2009 00:10:39 -0800
From:	Harvey Harrison <harvey.harrison@...il.com>
To:	Stefan Richter <stefanr@...6.in-berlin.de>
Cc:	righi.andrea@...il.com, Johannes Weiner <hannes@...xchg.org>,
	Dave Jones <davej@...hat.com>,
	Johannes Weiner <hannes@...urebad.de>,
	Krzysztof Helt <krzysztof.h1@...pl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fbmem: fix copy_from/to_user() with mutex held

On Mon, 2009-01-19 at 09:05 +0100, Stefan Richter wrote:
> Stefan Richter wrote:
> > Andrea Righi wrote:
> >> +struct fb_info *get_fb_info(struct fb_info *info)
> >> +__acquires(&info->lock)
> >> +{
> >> +	mutex_lock(&info->lock);
> >> +	if (!info->fbops) {
> >> +		mutex_unlock(&info->lock);
> >> +		return NULL;
> >> +	}
> >> +	return info;
> >> +}
> >> +
> >> +void put_fb_info(struct fb_info *info)
> >> +__releases(&info->lock)
> >> +{
> >> +	mutex_unlock(&info->lock);
> >> +}
> >> +
> > 
> > These are IMO bad function names.
> 
> PS:  The return value of the mutex_lock wrapper is also bad.  A bool or
> int would IMO be clearer, similar to the return value of mutex_trylock.

That, and there is no possible way to get the sparse annotations right
for that function, which means you'll get no help from sparse in lock
checking.

So I'd suggest just opencoding these where needed instead of the
wrappers.

Harvey

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