netconsole: convert to NBCON console infrastructure

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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/ [1]
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20260206-nbcon-v7-3-62bda69b1b41@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

...

This commit is contained in:

Breno Leitao 2026-02-06 04:45:31 -08:00 • committed by Jakub Kicinski

parent eaf35bc63b

commit 7eab73b186

1 changed files with 62 additions and 39 deletions

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drivers/net/netconsole.c

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