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-rw-r--r--debian/patches-rt/0007-printk-Properly-deal-with-nbcon-consoles-on-seq-init.patch116
1 files changed, 116 insertions, 0 deletions
diff --git a/debian/patches-rt/0007-printk-Properly-deal-with-nbcon-consoles-on-seq-init.patch b/debian/patches-rt/0007-printk-Properly-deal-with-nbcon-consoles-on-seq-init.patch
new file mode 100644
index 0000000000..cc54d0652e
--- /dev/null
+++ b/debian/patches-rt/0007-printk-Properly-deal-with-nbcon-consoles-on-seq-init.patch
@@ -0,0 +1,116 @@
+From: John Ogness <john.ogness@linutronix.de>
+Date: Wed, 22 Nov 2023 11:23:43 +0000
+Subject: [PATCH 07/48] printk: Properly deal with nbcon consoles on seq init
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.8/older/patches-6.8.2-rt11.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
+not updated for nbcon consoles.
+
+Check if it is an nbcon boot console and if so call
+nbcon_seq_read() to read seq.
+
+Also setup the nbcon sequence number and reset the legacy
+sequence number from register_console() (rather than in
+nbcon_init() and nbcon_seq_force()). This removes all legacy
+sequence handling from nbcon.c so the code is easier to follow
+and maintain.
+
+Signed-off-by: John Ogness <john.ogness@linutronix.de>
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ kernel/printk/nbcon.c | 7 +------
+ kernel/printk/printk.c | 29 ++++++++++++++++++++++++-----
+ 2 files changed, 25 insertions(+), 11 deletions(-)
+
+--- a/kernel/printk/nbcon.c
++++ b/kernel/printk/nbcon.c
+@@ -172,9 +172,6 @@ void nbcon_seq_force(struct console *con
+ u64 valid_seq = max_t(u64, seq, prb_first_valid_seq(prb));
+
+ atomic_long_set(&ACCESS_PRIVATE(con, nbcon_seq), __u64seq_to_ulseq(valid_seq));
+-
+- /* Clear con->seq since nbcon consoles use con->nbcon_seq instead. */
+- con->seq = 0;
+ }
+
+ /**
+@@ -964,8 +961,6 @@ bool nbcon_alloc(struct console *con)
+ *
+ * nbcon_alloc() *must* be called and succeed before this function
+ * is called.
+- *
+- * This function expects that the legacy @con->seq has been set.
+ */
+ void nbcon_init(struct console *con)
+ {
+@@ -974,7 +969,7 @@ void nbcon_init(struct console *con)
+ /* nbcon_alloc() must have been called and successful! */
+ BUG_ON(!con->pbufs);
+
+- nbcon_seq_force(con, con->seq);
++ nbcon_seq_force(con, 0);
+ nbcon_state_set(con, &state);
+ }
+
+--- a/kernel/printk/printk.c
++++ b/kernel/printk/printk.c
+@@ -3353,6 +3353,7 @@ static void try_enable_default_console(s
+ newcon->flags |= CON_CONSDEV;
+ }
+
++/* Set @newcon->seq to the first record this console should print. */
+ static void console_init_seq(struct console *newcon, bool bootcon_registered)
+ {
+ struct console *con;
+@@ -3401,11 +3402,20 @@ 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;
+ }
+ }
+
+@@ -3522,9 +3532,18 @@ void register_console(struct console *ne
+ newcon->dropped = 0;
+ console_init_seq(newcon, bootcon_registered);
+
+- if (newcon->flags & CON_NBCON)
++ if (newcon->flags & CON_NBCON) {
+ nbcon_init(newcon);
+
++ /*
++ * nbcon consoles have their own sequence counter. The legacy
++ * sequence counter is reset so that it is clear it is not
++ * being used.
++ */
++ nbcon_seq_force(newcon, newcon->seq);
++ newcon->seq = 0;
++ }
++
+ /*
+ * Put this console in the list - keep the
+ * preferred driver at the head of the list.