linux-kernel - Re: [PATCH tip/core/rcu 02/13] lockdep: Use "WARNING" tag on lockdep splats

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Date:   Thu, 13 Apr 2017 11:14:18 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, mingo@...nel.org,
        jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, rostedt@...dmis.org,
        dhowells@...hat.com, edumazet@...gle.com, fweisbec@...il.com,
        oleg@...hat.com, bobby.prani@...il.com
Subject: Re: [PATCH tip/core/rcu 02/13] lockdep: Use "WARNING" tag on lockdep
 splats

On Wed, Apr 12, 2017 at 09:55:38AM -0700, Paul E. McKenney wrote:
> This commit changes lockdep splats to begin lines with "WARNING" and
> to use pr_warn() instead of printk().  This change eases scripted
> analysis of kernel console output.
> 
> Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
> Reported-by: Ingo Molnar <mingo@...nel.org>
> Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> Acked-by: Dmitry Vyukov <dvyukov@...gle.com>
> ---
>  kernel/locking/lockdep.c       | 86 +++++++++++++++++++++---------------------
>  kernel/locking/rtmutex-debug.c |  9 +++--
>  2 files changed, 48 insertions(+), 47 deletions(-)
> 
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index a95e5d1f4a9c..e9d4f85b290c 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -1144,10 +1144,10 @@ print_circular_bug_header(struct lock_list *entry, unsigned int depth,
>  		return 0;
>  
>  	printk("\n");
> -	printk("======================================================\n");
> -	printk("[ INFO: possible circular locking dependency detected ]\n");
> +	pr_warn("======================================================\n");
> +	pr_warn("WARNING: possible circular locking dependency detected\n");
>  	print_kernel_ident();
> -	printk("-------------------------------------------------------\n");
> +	pr_warn("------------------------------------------------------\n");
>  	printk("%s/%d is trying to acquire lock:\n",
>  		curr->comm, task_pid_nr(curr));
>  	print_lock(check_src);

Blergh, not a fan of this patch. Now we have an odd mix of pr_crap() and
printk().