linux-kernel - Re: Top kernel oopses/warnings this week

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Date:	Mon, 17 Dec 2007 16:21:12 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Arjan van de Ven <arjan@...ux.intel.com>
cc:	Tony Luck <tony.luck@...el.com>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>, protasnb@...il.com,
	tytso@...nk.org
Subject: Re: Top kernel oopses/warnings this week



On Mon, 17 Dec 2007, Arjan van de Ven wrote:
>
> +char *get_boot_uuid(void)
> +{
> +	static char target[38];
> +	unsigned char *uuid;
> +
> +	if (sysctl_bootid[8] == 0)
> +		generate_random_uuid(sysctl_bootid);
> +	/* sysctl_bootid is signed, to print we need unsigned .. */
> +	uuid = sysctl_bootid;
> +
> +	if (target[0] == 0) {
> +		sprintf(target, "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-"
> +			"%02x%02x%02x%02x%02x%02x",

Why isn't *everything* inside that "if (target[0] == 0" check?

IOW, that function should look something like

	const char *get_boot_uuid(void)
	{
		static char target[38];

		if (!target[0])
			fill_boot_uid(target)
		return target;
	}

which also allows you to clean it up a bit.

I'd _also_ suggest that you'd actually try to avoid that horrid sequence 
of "%02x..", and instead just make sure that sysctl_bootid[] is 4-byte 
aligned, and then you can do

	sprintf("%08x-%04x-%04x-%04x-%04x%08x",
		ntohl(0[(u32 *)uuid]),
		ntohs(2[(u16 *)uuid]),
		ntohs(3[(u16 *)uuid]),
		ntohs(4[(u16 *)uuid]),
		ntohs(5[(u16 *)uuid]),
		ntohl(3[(u32 *)uuid]));

which also gets bonus points for being totally unreadable, and thus 100% 
in the spirit of uuid's.

		Linus
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