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-rw-r--r--debian/patches-rt/0107-printk-add-console-handover.patch76
1 files changed, 76 insertions, 0 deletions
diff --git a/debian/patches-rt/0107-printk-add-console-handover.patch b/debian/patches-rt/0107-printk-add-console-handover.patch
new file mode 100644
index 000000000..9abc4efd5
--- /dev/null
+++ b/debian/patches-rt/0107-printk-add-console-handover.patch
@@ -0,0 +1,76 @@
+From ead093d95a7917fa12f9d4653032eac383d21c1d Mon Sep 17 00:00:00 2001
+From: John Ogness <john.ogness@linutronix.de>
+Date: Mon, 30 Nov 2020 01:42:09 +0106
+Subject: [PATCH 107/323] printk: add console handover
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz
+
+If earlyprintk is used, a boot console will print directly to the
+console immediately. The boot console will unregister itself as soon
+as a non-boot console registers. However, the non-boot console does
+not begin printing until its kthread has started. Since this happens
+much later, there is a long pause in the console output. If the
+ringbuffer is small, messages could even be dropped during the
+pause.
+
+Add a new CON_HANDOVER console flag to be used internally by printk
+in order to track which non-boot console took over from a boot
+console. If handover consoles have implemented write_atomic(), they
+are allowed to print directly to the console until their kthread can
+take over.
+
+Signed-off-by: John Ogness <john.ogness@linutronix.de>
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ include/linux/console.h | 1 +
+ kernel/printk/printk.c | 8 +++++++-
+ 2 files changed, 8 insertions(+), 1 deletion(-)
+
+diff --git a/include/linux/console.h b/include/linux/console.h
+index 3e99359e0660..027278792eea 100644
+--- a/include/linux/console.h
++++ b/include/linux/console.h
+@@ -138,6 +138,7 @@ static inline int con_debug_leave(void)
+ #define CON_ANYTIME (16) /* Safe to call when cpu is offline */
+ #define CON_BRL (32) /* Used for a braille device */
+ #define CON_EXTENDED (64) /* Use the extended output format a la /dev/kmsg */
++#define CON_HANDOVER (128) /* Device was previously a boot console. */
+
+ struct console {
+ char name[16];
+diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
+index 2b110b9ae34a..58da007d7c99 100644
+--- a/kernel/printk/printk.c
++++ b/kernel/printk/printk.c
+@@ -1729,6 +1729,8 @@ static bool console_can_sync(struct console *con)
+ return false;
+ if (con->write_atomic && kernel_sync_mode())
+ return true;
++ if (con->write_atomic && (con->flags & CON_HANDOVER) && !con->thread)
++ return true;
+ if (con->write && (con->flags & CON_BOOT) && !con->thread)
+ return true;
+ return false;
+@@ -1740,6 +1742,8 @@ static bool call_sync_console_driver(struct console *con, const char *text, size
+ return false;
+ if (con->write_atomic && kernel_sync_mode())
+ con->write_atomic(con, text, text_len);
++ else if (con->write_atomic && (con->flags & CON_HANDOVER) && !con->thread)
++ con->write_atomic(con, text, text_len);
+ else if (con->write && (con->flags & CON_BOOT) && !con->thread)
+ con->write(con, text, text_len);
+ else
+@@ -2832,8 +2836,10 @@ void register_console(struct console *newcon)
+ * the real console are the same physical device, it's annoying to
+ * see the beginning boot messages twice
+ */
+- if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
++ if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
+ newcon->flags &= ~CON_PRINTBUFFER;
++ newcon->flags |= CON_HANDOVER;
++ }
+
+ /*
+ * Put this console in the list - keep the
+--
+2.43.0
+