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68 lines
2.7 KiB
Diff
68 lines
2.7 KiB
Diff
From: John Ogness <john.ogness@linutronix.de>
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Date: Mon, 30 Nov 2020 01:42:09 +0106
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Subject: [PATCH 27/28] printk: add console handover
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If earlyprintk is used, a boot console will print directly to the
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console immediately. The boot console will unregister itself as soon
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as a non-boot console registers. However, the non-boot console does
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not begin printing until its kthread has started. Since this happens
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much later, there is a long pause in the console output. If the
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ringbuffer is small, messages could even be dropped during the
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pause.
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Add a new CON_HANDOVER console flag to be used internally by printk
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in order to track which non-boot console took over from a boot
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console. If handover consoles have implemented write_atomic(), they
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are allowed to print directly to the console until their kthread can
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take over.
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Signed-off-by: John Ogness <john.ogness@linutronix.de>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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include/linux/console.h | 1 +
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kernel/printk/printk.c | 8 +++++++-
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2 files changed, 8 insertions(+), 1 deletion(-)
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--- a/include/linux/console.h
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+++ b/include/linux/console.h
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@@ -137,6 +137,7 @@ static inline int con_debug_leave(void)
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#define CON_ANYTIME (16) /* Safe to call when cpu is offline */
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#define CON_BRL (32) /* Used for a braille device */
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#define CON_EXTENDED (64) /* Use the extended output format a la /dev/kmsg */
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+#define CON_HANDOVER (128) /* Device was previously a boot console. */
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struct console {
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char name[16];
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--- a/kernel/printk/printk.c
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+++ b/kernel/printk/printk.c
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@@ -1726,6 +1726,8 @@ static bool console_can_sync(struct cons
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return false;
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if (con->write_atomic && kernel_sync_mode())
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return true;
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+ if (con->write_atomic && (con->flags & CON_HANDOVER) && !con->thread)
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+ return true;
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if (con->write && (con->flags & CON_BOOT) && !con->thread)
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return true;
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return false;
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@@ -1737,6 +1739,8 @@ static bool call_sync_console_driver(str
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return false;
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if (con->write_atomic && kernel_sync_mode())
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con->write_atomic(con, text, text_len);
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+ else if (con->write_atomic && (con->flags & CON_HANDOVER) && !con->thread)
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+ con->write_atomic(con, text, text_len);
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else if (con->write && (con->flags & CON_BOOT) && !con->thread)
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con->write(con, text, text_len);
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else
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@@ -2829,8 +2833,10 @@ void register_console(struct console *ne
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* the real console are the same physical device, it's annoying to
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* see the beginning boot messages twice
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*/
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- if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
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+ if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
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newcon->flags &= ~CON_PRINTBUFFER;
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+ newcon->flags |= CON_HANDOVER;
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+ }
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/*
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* Put this console in the list - keep the
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