Re: [PATCH -v2 2/3] ACPI, APEI, Add APEI generic error status print support

Andrew Morton
2010-11-30T18:18:53Z

On Tue, 30 Nov 2010 10:00:47 -0800 "Luck, Tony" <tony.luck@intel.com> wrote:

> > + for (i = 0; i < strs_size; i++) {
> > + if (!(bits & (1U << i)))
> > + continue;
> > + str = strs[i];
> > + if (len && len + strlen(str) + 2 > 80) {
> > + printk("\n");
> > + len = 0;
> > + }
> > + if (!len)
> > + len = pr_pfx(pfx, "%s", str);
> > + else
> > + len += printk(", %s", str);
> > + }
> > + if (len)
> > + printk("\n");
>
> Does printk() offer any guarantees about getting all the characters
> from a single printk() call out to the console without interleaving
> with messages from printk() calls on other cpus?

Yes, it uses logbuf_lock to atomically append all the output from a
printk into log_buf[]. Then it calls the console drivers against
log_buf[]. It's hard to see how a console driver could then screw that
up.

> If it does, then
> it would be a good idea to sprintf() the parts of this message to
> a buffer and then use one printk() call.

yup.

> I think I read that netconsole
> ends up with one packet on the wire for each call to printk().
>
> Trying to parse output jumbled together from multiple cpus
> doesn't sound like fun.
>
> -Tony