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From: John Ogness <john.ogness@linutronix.de>
Date: Tue, 12 Feb 2019 15:29:47 +0100
Subject: [PATCH 09/25] printk: remove exclusive console hack
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.4/older/patches-5.4.13-rt7.tar.xz
In order to support printing the printk log history when new
consoles are registered, a global exclusive_console variable is
temporarily set. This only works because printk runs with
preemption disabled.
When console printing is moved to a fully preemptible dedicated
kthread, this hack no longer works.
Remove exclusive_console usage.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
kernel/printk/printk.c | 30 ++++--------------------------
1 file changed, 4 insertions(+), 26 deletions(-)
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -269,11 +269,6 @@ static void __up_console_sem(unsigned lo
static int console_locked, console_suspended;
/*
- * If exclusive_console is non-NULL then only this console is to be printed to.
- */
-static struct console *exclusive_console;
-
-/*
* Array of consoles built from command line options (console=)
*/
@@ -443,7 +438,6 @@ static u32 log_next_idx;
/* the next printk record to write to the console */
static u64 console_seq;
static u32 console_idx;
-static u64 exclusive_console_stop_seq;
/* the next printk record to read after the last 'clear' command */
static u64 clear_seq;
@@ -1815,8 +1809,6 @@ static void call_console_drivers(const c
return;
for_each_console(con) {
- if (exclusive_console && con != exclusive_console)
- continue;
if (!(con->flags & CON_ENABLED))
continue;
if (!con->write)
@@ -2109,7 +2101,6 @@ static u64 syslog_seq;
static u32 syslog_idx;
static u64 console_seq;
static u32 console_idx;
-static u64 exclusive_console_stop_seq;
static u64 log_first_seq;
static u32 log_first_idx;
static u64 log_next_seq;
@@ -2478,12 +2469,6 @@ void console_unlock(void)
goto skip;
}
- /* Output to all consoles once old messages replayed. */
- if (unlikely(exclusive_console &&
- console_seq >= exclusive_console_stop_seq)) {
- exclusive_console = NULL;
- }
-
len += msg_print_text(msg,
console_msg_format & MSG_FORMAT_SYSLOG,
printk_time, text + len, sizeof(text) - len);
@@ -2811,17 +2796,6 @@ void register_console(struct console *ne
logbuf_lock_irqsave(flags);
console_seq = syslog_seq;
console_idx = syslog_idx;
- /*
- * We're about to replay the log buffer. Only do this to the
- * just-registered console to avoid excessive message spam to
- * the already-registered consoles.
- *
- * Set exclusive_console with disabled interrupts to reduce
- * race window with eventual console_flush_on_panic() that
- * ignores console_lock.
- */
- exclusive_console = newcon;
- exclusive_console_stop_seq = console_seq;
logbuf_unlock_irqrestore(flags);
}
console_unlock();
@@ -2833,6 +2807,10 @@ void register_console(struct console *ne
* boot consoles, real consoles, etc - this is to ensure that end
* users know there might be something in the kernel's log buffer that
* went to the bootconsole (that they do not see on the real console)
+ *
+ * This message is also important because it will trigger the
+ * printk kthread to begin dumping the log buffer to the newly
+ * registered console.
*/
pr_info("%sconsole [%s%d] enabled\n",
(newcon->flags & CON_BOOT) ? "boot" : "" ,
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