[PATCH RT] kernel/printk: Don't try to print from IRQ/NMI region

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

On -RT we try to acquire sleeping locks which might lead to warnings
from lockdep or a warn_on() from spin_try_lock() (which is a rtmutex on
RT).
We don't print in general from a IRQ off region so we should not try
this via console_unblank() / bust_spinlocks() as well.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 kernel/printk/printk.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1502,6 +1502,11 @@ static void call_console_drivers(int lev
 	if (!console_drivers)
 		return;
 
+	if (IS_ENABLED(CONFIG_PREEMPT_RT_BASE)) {
+		if (in_irq() || in_nmi())
+			return;
+	}
+
 	migrate_disable();
 	for_each_console(con) {
 		if (exclusive_console && con != exclusive_console)
@@ -2434,6 +2439,11 @@ void console_unblank(void)
 {
 	struct console *c;
 
+	if (IS_ENABLED(CONFIG_PREEMPT_RT_BASE)) {
+		if (in_irq() || in_nmi())
+			return;
+	}
+
 	/*
 	 * console_unblank can no longer be called in interrupt context unless
 	 * oops_in_progress is set to 1..