[tip: sched/rt] printk: Track nbcon consoles

["tip-bot2 for John Ogness" <tip-bot2@linutronix.de>]

The following commit has been merged into the sched/rt branch of tip:

Commit-ID:     bebd87ae27e052e390c203893c7ee46f54b0bf9e
Gitweb:        https://git.kernel.org/tip/bebd87ae27e052e390c203893c7ee46f54b0bf9e
Author:        John Ogness <john.ogness@linutronix.de>
AuthorDate:    Tue, 20 Aug 2024 08:35:54 +02:06
Committer:     Petr Mladek <pmladek@suse.com>
CommitterDate: Wed, 21 Aug 2024 14:56:25 +02:00

printk: Track nbcon consoles

Add a global flag @have_nbcon_console to identify if any nbcon
consoles are registered. This will be used in follow-up commits
to preserve legacy behavior when no nbcon consoles are registered.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-29-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
---
 kernel/printk/printk.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index b3ddcf3..e30107d 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -471,6 +471,11 @@ static DEFINE_MUTEX(syslog_lock);
 static bool have_legacy_console;
 
 /*
+ * Specifies if an nbcon console is registered.
+ */
+static bool have_nbcon_console;
+
+/*
  * Specifies if a boot console is registered. If boot consoles are present,
  * nbcon consoles cannot print simultaneously and must be synchronized by
  * the console lock. This is because boot consoles and nbcon consoles may
@@ -3638,6 +3643,7 @@ void register_console(struct console *newcon)
 	init_seq = get_init_console_seq(newcon, bootcon_registered);
 
 	if (newcon->flags & CON_NBCON) {
+		have_nbcon_console = true;
 		nbcon_seq_force(newcon, init_seq);
 	} else {
 		have_legacy_console = true;
@@ -3718,6 +3724,7 @@ static int unregister_console_locked(struct console *console)
 {
 	bool use_device_lock = (console->flags & CON_NBCON) && console->write_atomic;
 	bool found_legacy_con = false;
+	bool found_nbcon_con = false;
 	bool found_boot_con = false;
 	unsigned long flags;
 	struct console *c;
@@ -3785,13 +3792,18 @@ static int unregister_console_locked(struct console *console)
 	for_each_console(c) {
 		if (c->flags & CON_BOOT)
 			found_boot_con = true;
-		if (!(c->flags & CON_NBCON))
+
+		if (c->flags & CON_NBCON)
+			found_nbcon_con = true;
+		else
 			found_legacy_con = true;
 	}
 	if (!found_boot_con)
 		have_boot_console = found_boot_con;
 	if (!found_legacy_con)
 		have_legacy_console = found_legacy_con;
+	if (!found_nbcon_con)
+		have_nbcon_console = found_nbcon_con;
 
 	return res;
 }