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

Joe Perches
2017-08-30T01:52:44Z

On Tue, 2017-08-29 at 21:10 -0400, Steven Rostedt wrote:
> On Wed, 30 Aug 2017 10:03:48 +0900
> Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> wrote:
>
> > Hello,
> >
> > On (08/29/17 19:50), Steven Rostedt wrote:
> > [..]
> > > > A private buffer has none of those issues.
> > >
> > > What about using the seq_buf*() then?
> > >
> > > struct seq_buf s;
> > >
> > > buf = kmalloc(mysize);
> > > seq_buf_init(&s, buf, mysize);
> > >
> > > seq_printf(&s,"blah blah %d", bah_blah);
> > > [...]
> > > seq_printf(&s, "my last print\n");
> > >
> > > printk("%.*s", s.len, s.buffer);
> > >
> > > kfree(buf);
> >
> > could do. for a single continuation line printk("%.*s", s.len, s.buffer)
> > this will work perfectly fine. for a more general case - backtraces, dumps,
> > etc. - this requires some tweaks.
>
> We could simply add a seq_buf_printk() that is implemented in the printk
> proper, to parse the seq_buf buffer properly, and add the timestamps and
> such.

No need. printk would already add timestamps.

One addition might be to add a bit to initialize
the buffer so that printk("%s", s->buffer) is simpler.
---
diff --git a/include/linux/seq_buf.h b/include/linux/seq_buf.h
index fb7eb9ccb1cd..fb6c9de0ee33 100644
--- a/include/linux/seq_buf.h
+++ b/include/linux/seq_buf.h
@@ -26,6 +26,7 @@ static inline void seq_buf_clear(struct seq_buf *s)
{
s->len = 0;
s->readpos = 0;
+ *s->buffer = 0;
}

static inline void