[PATCH printk v2 05/18] printk: Atomic print in printk context on shutdown

[John Ogness]

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@xxxxxxxxxxxxx>
---
 kernel/printk/nbcon.c  | 5 +++--
 kernel/printk/printk.c | 7 ++++++-
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c
index 89b340ca303c..19f0db6945e4 100644
--- a/kernel/printk/nbcon.c
+++ b/kernel/printk/nbcon.c
@@ -1297,7 +1297,8 @@ static void nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq,
 	 * 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 *con)
 	 */
 	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);
 	}
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 137bd9a721c4..b58db15d2033 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2389,12 +2389,17 @@ asmlinkage int vprintk_emit(int facility, int level,
 		 *
 		 * - 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) {
-- 
2.39.2