Re: Top kernel oopses/warnings this week

Arjan van de Ven
2007-12-18T00:46:39Z

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.