diff options
Diffstat (limited to 'features/rt/printk-add-console-handover.patch')
| -rw-r--r-- | features/rt/printk-add-console-handover.patch | 75 |
1 files changed, 75 insertions, 0 deletions
diff --git a/features/rt/printk-add-console-handover.patch b/features/rt/printk-add-console-handover.patch new file mode 100644 index 00000000..bb55e3b1 --- /dev/null +++ b/features/rt/printk-add-console-handover.patch @@ -0,0 +1,75 @@ +From a87105bd119478687e8f73298fd74f6594f922ad 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 032/191] printk: add console handover + +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 b370e37a6d49..69bfff368294 100644 +--- a/include/linux/console.h ++++ b/include/linux/console.h +@@ -137,6 +137,7 @@ 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 d1b25ac5c73b..ee34245bf08a 100644 +--- a/kernel/printk/printk.c ++++ b/kernel/printk/printk.c +@@ -1726,6 +1726,8 @@ 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; +@@ -1737,6 +1739,8 @@ 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 +@@ -2829,8 +2833,10 @@ 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 +-- +2.19.1 + |