linux-kernel - Re: [PATCH tip/core/rcu 02/20] lockdep: Make RCU suspicious-access splats use pr

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Message-Id: <20170117010630.GX5238@linux.vnet.ibm.com>
Date:   Mon, 16 Jan 2017 17:06:30 -0800
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Josh Triplett <josh@...htriplett.org>
Cc:     linux-kernel@...r.kernel.org, mingo@...nel.org,
        jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org,
        dhowells@...hat.com, edumazet@...gle.com, dvhart@...ux.intel.com,
        fweisbec@...il.com, oleg@...hat.com, bobby.prani@...il.com
Subject: Re: [PATCH tip/core/rcu 02/20] lockdep: Make RCU suspicious-access
 splats use pr_err

On Sun, Jan 15, 2017 at 11:53:02PM -0800, Josh Triplett wrote:
> On Sat, Jan 14, 2017 at 01:13:03AM -0800, Paul E. McKenney wrote:
> > 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@...gle.com>
> > Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> 
> One comment below.

Good catch, fixed!

							Thanx, Paul

> >  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 7c38f8f3d97b..844cd04bb453 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("suspicious RCU usage. ]\n");
> 
> This message change seems unrelated, and potentially unintentional.
> 
> >  	print_kernel_ident();
> > -	printk("-------------------------------\n");
> > -	printk("%s:%d %s!\n", file, line, s);
> > -	printk("\nother info that might help us debug this:\n\n");
> > -	printk("\n%srcu_scheduler_active = %d, debug_locks = %d\n",
> > +	pr_err("-------------------------------\n");
> > +	pr_err("%s:%d %s!\n", file, line, s);
> > +	pr_err("\nother info that might help us debug this:\n\n");
> > +	pr_err("\n%srcu_scheduler_active = %d, debug_locks = %d\n",
> >  	       !rcu_lockdep_current_cpu_online()
> >  			? "RCU used illegally from offline CPU!\n"
> >  			: !rcu_is_watching()
> > -- 
> > 2.5.2
> > 
>