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From: John Ogness <john.ogness@linutronix.de>
Date: Mon, 23 Oct 2023 17:43:48 +0000
Subject: [PATCH 32/48] printk: Atomic print in printk context on shutdown
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.10/older/patches-6.10.2-rt14.tar.xz
For nbcon consoles, normally the printing is handled by the
dedicated console printing threads. However, on shutdown the
printing threads may not get a chance to print the final
messages.
When shutting down or rebooting (system_state > SYSTEM_RUNNING),
perform atomic printing from the printk() caller context.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
kernel/printk/nbcon.c | 5 +++--
kernel/printk/printk.c | 7 ++++++-
2 files changed, 9 insertions(+), 3 deletions(-)
--- a/kernel/printk/nbcon.c
+++ b/kernel/printk/nbcon.c
@@ -1297,7 +1297,8 @@ static void nbcon_atomic_flush_pending_c
* context must flush those remaining records if the printer thread
* is not available do it.
*/
- if (!con->kthread && prb_read_valid(prb, nbcon_seq_read(con), NULL)) {
+ if ((!con->kthread || (system_state > SYSTEM_RUNNING)) &&
+ prb_read_valid(prb, nbcon_seq_read(con), NULL)) {
stop_seq = prb_next_reserve_seq(prb);
goto again;
}
@@ -1639,7 +1640,7 @@ void nbcon_device_release(struct console
*/
cookie = console_srcu_read_lock();
if (console_is_usable(con, console_srcu_read_flags(con)) &&
- !con->kthread &&
+ (!con->kthread || (system_state > SYSTEM_RUNNING)) &&
prb_read_valid(prb, nbcon_seq_read(con), NULL)) {
__nbcon_atomic_flush_pending_con(con, prb_next_reserve_seq(prb), false);
}
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2389,12 +2389,17 @@ asmlinkage int vprintk_emit(int facility
*
* - When this CPU is in panic.
*
+ * - During shutdown, since the printing threads may not get
+ * a chance to print the final messages.
+ *
* Note that if boot consoles are registered, the console
* lock/unlock dance must be relied upon instead because nbcon
* consoles cannot print simultaneously with boot consoles.
*/
- if (is_panic_context)
+ if (is_panic_context ||
+ (system_state > SYSTEM_RUNNING)) {
nbcon_atomic_flush_pending();
+ }
}
if (do_trylock_unlock) {
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