Re: Top kernel oopses/warnings this week

[Arjan van de Ven]

Linus Torvalds wrote:
> 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?

the sysctl_bootid is shared with the /proc exposed bootid, so I need to generate it the same way

> 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.

again.. this is for compatibility with /proc/sys/kernel/random/boot_id .. the code 10 lines below my patch is identical and does
the %02x stuff... I didn't make that up, I just copied that to get the same output.
I can deviate for cleanup... but I can see some value of being the same format and same data.


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