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

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Date:   Tue, 31 Jan 2017 09:09:32 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>, Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-tip-commits@...r.kernel.org
Subject: Re: [tip:core/rcu] lockdep: Make RCU suspicious-access splats use pr_err

On Tue, Jan 31, 2017 at 8:54 AM, tip-bot for Paul E. McKenney
<tipbot@...or.com> wrote:
> Commit-ID:  4d4f88fa235f7f9ef8213564dc1804144332238b
> Gitweb:     http://git.kernel.org/tip/4d4f88fa235f7f9ef8213564dc1804144332238b
> Author:     Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> AuthorDate: Sat, 5 Nov 2016 04:17:15 -0700
> Committer:  Paul E. McKenney <paulmck@...ux.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@...gle.com>
> Signed-off-by: Paul E. McKenney <paulmck@...ux.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

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?).


>         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()