linux-kernel - Re: [PATCH] printk: Make console tracepoint safe in NMI() context

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Message-ID: <20220715110248.02b294b7@gandalf.local.home>
Date:   Fri, 15 Jul 2022 11:02:48 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Petr Mladek <pmladek@...e.com>
Cc:     "Paul E . McKenney" <paulmck@...nel.org>,
        John Ogness <john.ogness@...utronix.de>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Marco Elver <elver@...gle.com>, kasan-dev@...glegroups.com,
        Thomas Gleixner <tglx@...utronix.de>,
        Johannes Berg <johannes.berg@...el.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Naresh Kamboju <naresh.kamboju@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Linux Kernel Functional Testing <lkft@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] printk: Make console tracepoint safe in NMI() context

On Fri, 15 Jul 2022 14:01:52 +0200
Petr Mladek <pmladek@...e.com> wrote:

> +	/*
> +	 * trace_console_rcuidle() is not working in NMI. printk()
> +	 * is used more often in NMI than in rcuidle context.
> +	 * Choose the less evil solution here.
> +	 *
> +	 * raw_smp_processor_id() is reliable in rcuidle context.
> +	 */
> +	TP_CONDITION(!rcu_is_idle_cpu(raw_smp_processor_id())),
> +

As Marco mentioned in the other thread, would a check for
'rcu_is_watching()' be better?

-- Steve


>  	TP_STRUCT__entry(
>  		__dynamic_array(char, msg, len + 1)
>  	),