[PATCH net-next v2 3/5] netconsole: convert to NBCON console infrastructure
From: Breno Leitao <leitao@debian.org>
Date: 2026-01-20 18:16:11
Also in:
lkml
Subsystem:
netconsole, networking drivers, the rest · Maintainers:
Breno Leitao, Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
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
index dc3bd7c9b0498..c5d7e97fe2a78 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c@@ -1709,22 +1709,6 @@ static void send_ext_msg_udp(struct netconsole_target *nt, const char *msg, sysdata_len); } -static void write_ext_msg(struct console *con, const char *msg, - unsigned int len) -{ - struct netconsole_target *nt; - unsigned long flags; - - if ((oops_only && !oops_in_progress) || list_empty(&target_list)) - return; - - spin_lock_irqsave(&target_list_lock, flags); - list_for_each_entry(nt, &target_list, list) - if (nt->extended && nt->enabled && netif_running(nt->np.dev)) - send_ext_msg_udp(nt, msg, len); - spin_unlock_irqrestore(&target_list_lock, flags); -} - static void send_msg_udp(struct netconsole_target *nt, const char *msg, unsigned int len) {
@@ -1739,29 +1723,62 @@ static void send_msg_udp(struct netconsole_target *nt, const char *msg, } } -static void write_msg(struct console *con, const char *msg, unsigned int len) +/** + * netconsole_write - Generic function to send a msg to all targets + * @wctxt: nbcon write context + * @extended: "true" for extended console mode + * + * Given an nbcon write context, send the message to the netconsole targets + */ +static void netconsole_write(struct nbcon_write_context *wctxt, bool extended) { - unsigned long flags; struct netconsole_target *nt; if (oops_only && !oops_in_progress) return; - /* Avoid taking lock and disabling interrupts unnecessarily */ - if (list_empty(&target_list)) - return; - spin_lock_irqsave(&target_list_lock, flags); list_for_each_entry(nt, &target_list, list) { - if (!nt->extended && nt->enabled && netif_running(nt->np.dev)) { - /* - * We nest this inside the for-each-target loop above - * so that we're able to get as much logging out to - * at least one target if we die inside here, instead - * of unnecessarily keeping all targets in lock-step. - */ - send_msg_udp(nt, msg, len); - } + if (nt->extended != extended || !nt->enabled || + !netif_running(nt->np.dev)) + continue; + + /* If nbcon_enter_unsafe() fails, just return given netconsole + * lost the ownership, and iterating over the targets will not + * be able to re-acquire. + */ + if (!nbcon_enter_unsafe(wctxt)) + return; + + if (extended) + send_ext_msg_udp(nt, wctxt->outbuf, wctxt->len); + else + send_msg_udp(nt, wctxt->outbuf, wctxt->len); + + nbcon_exit_unsafe(wctxt); } +} + +static void netconsole_write_ext(struct console *con __always_unused, + struct nbcon_write_context *wctxt) +{ + netconsole_write(wctxt, true); +} + +static void netconsole_write_basic(struct console *con __always_unused, + struct nbcon_write_context *wctxt) +{ + netconsole_write(wctxt, false); +} + +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); }
@@ -1924,15 +1941,21 @@ static void free_param_target(struct netconsole_target *nt) } static struct console netconsole_ext = { - .name = "netcon_ext", - .flags = CON_ENABLED | CON_EXTENDED, - .write = write_ext_msg, + .name = "netcon_ext", + .flags = CON_ENABLED | CON_EXTENDED | CON_NBCON | CON_NBCON_ATOMIC_UNSAFE, + .write_thread = netconsole_write_ext, + .write_atomic = netconsole_write_ext, + .device_lock = netconsole_device_lock, + .device_unlock = netconsole_device_unlock, }; static struct console netconsole = { - .name = "netcon", - .flags = CON_ENABLED, - .write = write_msg, + .name = "netcon", + .flags = CON_ENABLED | CON_NBCON | CON_NBCON_ATOMIC_UNSAFE, + .write_thread = netconsole_write_basic, + .write_atomic = netconsole_write_basic, + .device_lock = netconsole_device_lock, + .device_unlock = netconsole_device_unlock, }; static int __init init_netconsole(void)
--
2.47.3