From: John Ogness Date: Wed, 22 Nov 2023 11:23:43 +0000 Subject: [PATCH 099/134] printk: Consider nbcon boot consoles on seq init Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.6/older/patches-6.6.7-rt18.tar.xz 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 Signed-off-by: Sebastian Andrzej Siewior --- kernel/printk/printk.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3392,11 +3392,20 @@ static void console_init_seq(struct cons 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; } }