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SubjectRe: [tip:core/rcu] lockdep: Make RCU suspicious-access splats use pr_err

* Dmitry Vyukov <dvyukov@google.com> wrote:

> On Tue, Jan 31, 2017 at 8:54 AM, tip-bot for Paul E. McKenney
> <tipbot@zytor.com> wrote:
> > Commit-ID: 4d4f88fa235f7f9ef8213564dc1804144332238b
> > Gitweb: http://git.kernel.org/tip/4d4f88fa235f7f9ef8213564dc1804144332238b
> > Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > AuthorDate: Sat, 5 Nov 2016 04:17:15 -0700
> > Committer: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > CommitDate: Mon, 23 Jan 2017 11:31:54 -0800
> >
> > lockdep: Make RCU suspicious-access splats use pr_err
> >
> > This commit switches RCU suspicious-access splats use pr_err()
> > instead of the current INFO printk()s. This change makes it easier
> > to automatically classify splats.
> >
> > Reported-by: Dmitry Vyukov <dvyukov@google.com>
> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > ---
> > kernel/locking/lockdep.c | 12 ++++++------
> > 1 file changed, 6 insertions(+), 6 deletions(-)
> >
> > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> > index 7c38f8f..d9a698e 100644
> > --- a/kernel/locking/lockdep.c
> > +++ b/kernel/locking/lockdep.c
> > @@ -4412,13 +4412,13 @@ void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
> > #endif /* #ifdef CONFIG_PROVE_RCU_REPEATEDLY */
> > /* Note: the following can be executed concurrently, so be careful. */
> > printk("\n");
> > - printk("===============================\n");
> > - printk("[ INFO: suspicious RCU usage. ]\n");
> > + pr_err("===============================\n");
> > + pr_err("[ ERR: suspicious RCU usage. ]\n");
>
>
> Can we please make rcu reports look like all other kernel reports, e.g.:
>
> WARNING: suspicious RCU usage

It was a prettification/typographical concept, as this:

===============================
[ INFO: suspicious RCU usage. ]
===============================

looks better than this:

===========================
INFO: suspicious RCU usage.
===========================

> I.e. prefix with a standard prefix (BUG/WARNING) and remove the [ ]
> that are used only in rcu/lockdep reports (is there any particular
> idea behind using [ ] in these reports and nowhere else?).

So lockdep was the first subsystem who started using the INFO/WARNING style of
coherent warning messages, and it spread elsewhere from there I think, minus
typographical details.

Arguably this would look even nicer:

==============================
| INFO: suspicious RCU usage |
==============================

But I don't have very strong feelings about this and could live with this as well:

==========================
INFO: suspicious RCU usage
==========================

(note the lack of the full stop.)

Thanks,

Ingo

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