netdev - Re: [PATCH net-next v6 0/4] net: netconsole: convert to NBCON console infrastructure

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Message-ID: <87fr7gp0qb.fsf@jogness.linutronix.de>
Date: Thu, 05 Feb 2026 00:12:52 +0106
From: John Ogness <john.ogness@...utronix.de>
To: Breno Leitao <leitao@...ian.org>, Breno Leitao <leitao@...ian.org>,
 Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
 <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, pmladek@...e.com
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Steven Rostedt
 <rostedt@...dmis.org>, Sergey Senozhatsky <senozhatsky@...omium.org>,
 Andrew Morton <akpm@...ux-foundation.org>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, asantostc@...il.com, efault@....de,
 gustavold@...il.com, calvin@...nvd.org, jv@...sburgh.net,
 mpdesouza@...e.com, kernel-team@...a.com, Simon Horman <horms@...nel.org>
Subject: Re: [PATCH net-next v6 0/4] net: netconsole: convert to NBCON
 console infrastructure

On 2026-02-03, Breno Leitao <leitao@...ian.org> wrote:
> This series adds support for the nbcon (new buffer console) infrastructure
> to netconsole, enabling lock-free, priority-based console operations that
> are safer in crash scenarios.
>
> The implementation is introduced in three steps:
>
> 0) Extend printk to expose CPU and taskname (task->comm) where the
>    printk originated from. (Thanks John and Petr for the support in
>    getting this done)
> 1) Refactor the message fragmentation logic into a reusable helper function
> 2) Extend nbcon support to non-extended (basic) consoles using the same
>    infrastructure.
>
> The initial discussion about it appeared a while ago in [1], in order to
> solve Mike's HARDIRQ-safe -> HARDIRQ-unsafe lock order warning, and the root
> cause is that some hosts were calling IRQ unsafe locks from inside console
> lock.
>
> At that time, we didn't have the CON_NBCON_ATOMIC_UNSAFE yet. John
> kindly implemented CON_NBCON_ATOMIC_UNSAFE in 187de7c212e5 ("printk:
> nbcon: Allow unsafe write_atomic() for panic"), and now we can
> implement netconsole on top of nbcon.
>
> Important to note that netconsole continues to call netpoll and the
> network TX helpers with interrupt disable, given the TX are called with
> target_list_lock.
>
> Netdev maintainers, Petr suggested that this patchset goes through netdev[2]
>
> Link: https://lore.kernel.org/all/b2qps3uywhmjaym4mht2wpxul4yqtuuayeoq4iv4k3zf5wdgh3@tocu6c7mj4lt/ [1]
> Link: https://lore.kernel.org/all/aW9D5M0o9_8hdVvt@pathway.suse.cz/ [2]
>
> Signed-off-by: Breno Leitao <leitao@...ian.org>
>
> ---
> Changes in v6:
> - Do not select PRINTK_EXECUTION_CTX in NETCONSOLE_DYNAMIC (Jakub)
> - Do not make PRINTK_EXECUTION_CTX user visible (Jakub)

I am really sorry, but I failed to communicate what I meant about
introducing the CONSOLE_HAS_EXECUTION_CTX symbol.

As Jakub mentioned, NETCONSOLE_DYNAMIC should just directly select
PRINTK_EXECUTION_CTX and get rid of the CONSOLE_HAS_EXECUTION_CTX symbol
(like you had in v1).

I apologize for the confusion and wasted effort here.

John