linux-kernel - Re: [PATCH 1/1] omap: Ptr "isr_reg" tracked as NULL was dereferenced

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Date:	Tue, 05 Oct 2010 08:01:12 -0700
From:	Kevin Hilman <khilman@...prootsystems.com>
To:	balbi@...com
Cc:	Evgeny Kuznetsov <EXT-Eugeny.Kuznetsov@...ia.com>,
	"tony\@atomide.com" <tony@...mide.com>,
	"linux-omap\@vger.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	"akpm\@linux-foundation.org" <akpm@...ux-foundation.org>,
	"zmc\@lurian.net" <zmc@...ian.net>,
	"a.j.buxton\@gmail.com" <a.j.buxton@...il.com>
Subject: Re: [PATCH 1/1] omap: Ptr "isr_reg" tracked as NULL was dereferenced

Felipe Balbi <balbi@...com> writes:

> Hi,
>
> On Tue, Oct 05, 2010 at 03:42:10AM -0500, Evgeny Kuznetsov wrote:
>>+	if (!isr_reg) {
>>+		printk(KERN_ERR "FATAL: Incorrect GPIO method %i\n",
>>+				bank->method);
>>+		BUG();
>>+		}
>
> this could be simply:
>
> BUG_ON(!isr_reg);

WARN_ON is better.

A BUG() will panic the kernel and stop everything.  This is not an error
condition that should prevent the entire kernel from running.

>From asm-generic/bug.h:

/*
 * Don't use BUG() or BUG_ON() unless there's really no way out; one
 * example might be detecting data structure corruption in the middle
 * of an operation that can't be backed out of.  If the (sub)system
 * can somehow continue operating, perhaps with reduced functionality,
 * it's probably not BUG-worthy.
 *
 * If you're tempted to BUG(), think again:  is completely giving up
 * really the *only* solution?  There are usually better options, where
 * users don't need to reboot ASAP and can mostly shut down cleanly.
 */
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