Re: [PATCH 5/5] ring-buffer: fix printk output

Ingo Molnar
2009-04-29T07:22:37Z

* Andrew Morton <akpm@linux-foundation.org> wrote:

> On Wed, 29 Apr 2009 08:09:55 +0200 Ingo Molnar <mingo@elte.hu> wrote:
>
> >
> > * Andrew Morton <akpm@linux-foundation.org> wrote:
> >
> > > On Wed, 29 Apr 2009 07:43:59 +0200 Ingo Molnar <mingo@elte.hu> wrote:
> > >
> > > >
> > > > * Andrew Morton <akpm@linux-foundation.org> wrote:
> > > >
> > > > > On Wed, 29 Apr 2009 00:48:19 -0400 Steven Rostedt <rostedt@goodmis.org> wrote:
> > > > >
> > > > > > - printk_once(KERN_WARNING "Tracing recursion: depth[%d]:"
> > > > > > + printk_once(KERN_WARNING "Tracing recursion: depth[%ld]:"
> > > > >
> > > > > hrmph. I didn't know that printk_once() existed, and I should
> > > > > have known. I wonder how many other people don't know.
> > > >
> > > > Was posted to linux-next@vger.kernel.org.
> > >
> > > Well no wonder I didn't know about it.
> >
> > I (too?) think it's counter-productive that the linux-next list is
> > split out of lkml. I constantly fall into that trap: i get a
> > bugreport against one of our trees, i see that there's vger in the
> > Cc: list and mistake it for being Cc:-ed to lkml (all our trees are
> > developed on lkml and most of the bugreports come Cc:-ed to lkml)
> > but in reality it's Cc:-ed to linux-next which has a much smaller
> > audience. (which audience apparently does not even include you)
> >
> > If this email list fragmentation and the resoluting loss of
> > information bothers you too then please ask Stephen to move
> > linux-next mails to lkml (i've Cc:-ed Stephen) - it's not like it's
> > actually something separate ... today's linux-next messages are
> > tomorrow's lkml messages. Moving linux-next mails to lkml would
> > nicely improve the S/N ratio on lkml.
> >
>
> eh. Just auto-add lkml to tipbot-commit emails?

Yeah - the tip-commits-bot already has such a feature and we are
making use of it - but this commit predates it. So it was posted to
linux-next and the tip-commits list.

My larger point remains, about possibly embedding linux-next into
lkml. I couldnt think of a single linux-next mail that isnt relevant
to lkml. It's all about commits that are destined for upstream in
0-2.5 months.

> printk_once() is racy on smp and preempt btw ;)

Like WARN_ONCE() and WARN_ON_ONCE(). It's really an "oh crap"
facility, not for normal kernel messages.

Do we want to complicate them with locking and preemption - or
should we just concentrate on getting the "oh crap" message out to
the syslog (before it's possibly too late to get anything out)?

I have no strong opinion about it - but i tend to like the simpler
method most. printk + stack dumps themselves arent atomic to begin
with.

Ingo