Re: [PATCH] printk: Print cpu number along with time

Jiri Kosina
2014-04-24T22:12:13Z

On Thu, 24 Apr 2014, Greg Kroah-Hartman wrote:

> > +#ifdef CONFIG_PRINTK_CPU
> > + if (!buf)
> > + return snprintf(NULL, 0, "[%5lu.000000,%02x] ",
>
> %02x for a cpu? What happens on machines with 8k cpus?

Ummm ... what issue do you see here, Greg? It'll print 0x1f40, no?

> And is this really an issue? Debugging by using printk is fun, but not
> really something that people need to add a cpu number to. Why not just
> use a tracepoint in your code to get the needed information instead?

Well, if you have dmesg dump from panic that happens every other year, and
you have to do post-mortem analysis on it, I am pretty sure you would love
to be able to figure out how the stack traces would look like without
inter-CPU interleaving. And I am pretty sure you wouldn't want to
insert/enable a tracepoint and wait another two years for the bug to
trigger again.

--
Jiri Kosina
SUSE Labs