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

From: John Ogness <john.ogness@linutronix.de>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel@vger.kernel.org,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Andrew Morton <akpm@linux-foundation.org>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Stephen Boyd <swboyd@chromium.org>,
	Alexander Potapenko <glider@google.com>,
	Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH next v3 1/2] dump_stack: move cpu lock to printk.c
Date: Tue, 15 Jun 2021 23:39:23 +0206	[thread overview]
Message-ID: <8735tiq0d8.fsf@jogness.linutronix.de> (raw)
In-Reply-To: <20210615174947.32057-2-john.ogness@linutronix.de>

On 2021-06-15, John Ogness <john.ogness@linutronix.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