Re: printk: what is going on with additional newlines?

Sergey Senozhatsky
2017-08-30T02:44:41Z

On (08/29/17 19:31), Joe Perches wrote:
[..]
> > the idea is not to do printk() on that seq buffer at all, but to
> > log_store(), atomically, seq buffer messages
> >
> > spin_lock(&logbuf_lock)
> > while (offset < seq_buffer->len) {
> > ...
> > log_store(seq->buffer + offset);
> > ...
> > }
> > spin_unlock(&logbuf_unlock)
>
> Why?
>
> What's wrong with a simple printk?
> It'd still do a log_store.

sure, it will. but in separate logbuf entries, and between two
consequent printk calls on the same CPU a lot of stuff can happen:
IRQs->printks, rescheduling->printks, etc. etc. (not to mention
concurrent printks from other CPUs) so what people want to have is
to have a way to make several printks appear next to each other in
the logs (dmesg or serial log). Tetsuo wants this, for instance,
for OOM reports and backtraces. SCIS/ATA people want it as well.

-ss