diff mbox series

[printk,v2,04/26] printk: Consider nbcon boot consoles on seq init

Message ID 20240218185726.1994771-5-john.ogness@linutronix.de
State New
Headers
Series wire up write_atomic() printing |

Commit Message

John Ogness Feb. 18, 2024, 6:57 p.m. UTC 
  If a non-boot console is registering and boot consoles exist, the
consoles are flushed before being unregistered. This allows the
non-boot console to continue where the boot console left off.

If for whatever reason flushing fails, the lowest seq found from
any of the enabled boot consoles is used. Until now con->seq was
checked. However, if it is an nbcon boot console, the function
nbcon_seq_read() must be used to read seq because con->seq is
always 0.

Check if it is an nbcon boot console and if so call
nbcon_seq_read() to read seq.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
---
 kernel/printk/printk.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

Comments

Petr Mladek Feb. 20, 2024, 10:26 a.m. UTC | #1 
On Sun 2024-02-18 20:03:04, John Ogness wrote:
> If a non-boot console is registering and boot consoles exist, the
> consoles are flushed before being unregistered. This allows the
> non-boot console to continue where the boot console left off.
> 
> If for whatever reason flushing fails, the lowest seq found from
> any of the enabled boot consoles is used. Until now con->seq was
> checked. However, if it is an nbcon boot console, the function
> nbcon_seq_read() must be used to read seq because con->seq is
> always 0.

This says that con->seq is always 0.

> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -3391,11 +3391,20 @@ static void console_init_seq(struct console *newcon, bool bootcon_registered)
>  
>  				newcon->seq = prb_next_seq(prb);
>  				for_each_console(con) {
> -					if ((con->flags & CON_BOOT) &&
> -					    (con->flags & CON_ENABLED) &&
> -					    con->seq < newcon->seq) {
> -						newcon->seq = con->seq;
> +					u64 seq;
> +
> +					if (!((con->flags & CON_BOOT) &&
> +					      (con->flags & CON_ENABLED))) {
> +						continue;
>  					}
> +
> +					if (con->flags & CON_NBCON)
> +						seq = nbcon_seq_read(con);
> +					else
> +						seq = con->seq;
> +
> +					if (seq < newcon->seq)
> +						newcon->seq = seq;

But this sets con->seq to some value even for nbcon consoles.

It would make more sense to use nbcon_seq_force() for nbcon
consoles here and remove the copying from nbcon_init().

Otherwise, it looks good.

Best Regards,
Petr
diff mbox series

Patch

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 1685a71f3f71..696a9d76c09c 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3391,11 +3391,20 @@  static void console_init_seq(struct console *newcon, bool bootcon_registered)
 
 				newcon->seq = prb_next_seq(prb);
 				for_each_console(con) {
-					if ((con->flags & CON_BOOT) &&
-					    (con->flags & CON_ENABLED) &&
-					    con->seq < newcon->seq) {
-						newcon->seq = con->seq;
+					u64 seq;
+
+					if (!((con->flags & CON_BOOT) &&
+					      (con->flags & CON_ENABLED))) {
+						continue;
 					}
+
+					if (con->flags & CON_NBCON)
+						seq = nbcon_seq_read(con);
+					else
+						seq = con->seq;
+
+					if (seq < newcon->seq)
+						newcon->seq = seq;
 				}
 			}