linux-kernel - Re: [PATCH next v3 1/2] dump_stack: move cpu lock to printk.c

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Date:   Tue, 15 Jun 2021 23:39:23 +0206
From:   John Ogness <john.ogness@...utronix.de>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Stephen Boyd <swboyd@...omium.org>,
        Alexander Potapenko <glider@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH next v3 1/2] dump_stack: move cpu lock to printk.c

On 2021-06-15, John Ogness <john.ogness@...utronix.de> wrote:
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 114e9963f903..5369d8f33299 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -3532,3 +3532,70 @@ void kmsg_dump_rewind(struct kmsg_dump_iter *iter)
>  EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
>  
>  #endif
> +
> +#ifdef CONFIG_SMP
> +static atomic_t printk_cpulock_owner = ATOMIC_INIT(-1);
> +static bool printk_cpulock_nested;

I just realized that @printk_cpulock_nested will need to be an atomic_t
counter to allow multiple nested levels since nesting can also occur
because of recursion and not only because of an interrupting NMI
context. So a v4 will be needed for that simple change. But please still
comment on the rest.

Thanks.

John Ogness