On Fri, Jan 23, 2026 at 02:48:47AM -0800, Breno Leitao wrote:

Hello Simon!

On Thu, Jan 22, 2026 at 09:09:34PM +0000, Simon Horman wrote:

quoted

On Tue, Jan 20, 2026 at 08:23:49AM -0800, Breno Leitao wrote:

quoted

Convert netconsole from the legacy console API to the NBCON framework.
NBCON provides threaded printing which unblocks printk()s and flushes in
a thread, decoupling network TX from printk() when netconsole is
in use.

Since netconsole relies on the network stack which cannot safely operate
from all atomic contexts, mark both consoles with
CON_NBCON_ATOMIC_UNSAFE. (See discussion in [1])

CON_NBCON_ATOMIC_UNSAFE restricts write_atomic() usage to emergency
scenarios (panic) where regular messages are sent in threaded mode.

Implementation changes:
- Unify write_ext_msg() and write_msg() into netconsole_write()
- Add device_lock/device_unlock callbacks to manage target_list_lock
- Use nbcon_enter_unsafe()/nbcon_exit_unsafe() around network
  operations.
  - If nbcon_enter_unsafe() fails, just return given netconsole lost
    the ownership of the console.
- Set write_thread and write_atomic callbacks (both use same function)

Link: https://lore.kernel.org/all/b2qps3uywhmjaym4mht2wpxul4yqtuuayeoq4iv4k3zf5wdgh3@tocu6c7mj4lt/ (local) [1]
Signed-off-by: Breno Leitao <leitao@debian.org>
---
 drivers/net/netconsole.c | 97 ++++++++++++++++++++++++++++++------------------
 1 file changed, 60 insertions(+), 37 deletions(-)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c

...

quoted

+static void netconsole_device_lock(struct console *con __always_unused,
+				   unsigned long *flags)
+{
+	spin_lock_irqsave(&target_list_lock, *flags);
+}
+
+static void netconsole_device_unlock(struct console *con __always_unused,
+				     unsigned long flags)
+{
 	spin_unlock_irqrestore(&target_list_lock, flags);
 }
 

Hi Breno,

I'm wondering if we could consider the following annotations,
as "suggested" by Sparse[1].

This is great. I hadn't realized that Al Viro's sparse tree includes this
additional check, which is really useful.

Are you using Al Viro's branch rather than the sparse mainline?

(I'm asking to see if I should also follow master and do the same, in
true padawan fashion)

Well, I think it would be best if mainline was fixed.
(Although I am yet to do anything towards making that happen.)

But to answer your question, yes, I am using Al's tree.
Since a few days ago when I tracked down that it allows
Sparse to once work significantly more robustly on the
current Kernel tree.