On Tue, 2014-01-28 at 00:26 +0000, Luck, Tony wrote:
> > But that actually argues *more* for moving to a world where that
> > (common, but also often-forgotten) final '\n' at the end should be
> > de-emphasized. So I don't think it would be at all wrong to expect
> > that
> >
> > printk("Line A");
> > printk("Line B");
> >
> > should print two lines. We very much had that KERN_CONT to encode the
> > *exception* to this, for the (not very common) cases where we end up
> > listing multiple things on one line.
Depends on how old the code in question is.
KERN_CONT was introduced in Oct 2007 (commit 4749252776)
and everything older than that actually did have the
intention of continuing a previous line or was a
defect.
KERN_DEFAULT was June 2009 (commit e28d7137041) and
that allowed printks to start with any KERN_<LEVEL>
but KERN_CONT and actually start on a new line too
even if the preceding printk did not end in '\n'.
There are very few uses overall of KERN_DEFAULT.
I think KERN_DEFAULT should be removed actually.
All the uses might be better with a specific level.
> Of course if people *really* want things on the same line, they usually end
> up using sprintf() to save the individual pieces to some buffer and the dump
> that out using one printk() call
No, actually, they don't.
There's probably much more code that uses KERN_CONT
or no KERN_ level where it's intended that the printks
be merged than uses of intermediate buffers.
There are many uses of %pV that effectively serve as a
mechanism to avoid using multiple printks though.
> ... because KERN_CONT isn't much help when
> some other code comes along and drops its own output in the middle of
> what you were trying to pretty print.
Exactly true.
I've submitted quite a few patches that avoid multiple
printks by either using %pV or coalescing the separate
printks into a single printk.
There are _lots_ more that could be done.
Maybe adding a patch similar to what Linus proposes would
cause a lot more of these changes to be done quicker.
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