[PATCH RT 4/8] kernel/printk: Dont try to print from IRQ/NMI region

[Steven Rostedt]

3.10.102-rt113-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>

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@xxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 kernel/printk.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/kernel/printk.c b/kernel/printk.c
index 1b7fbc73c125..55b6871f21e2 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1302,6 +1302,11 @@ static void call_console_drivers(int level, const char *text, size_t len)
 	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)
@@ -2236,6 +2241,11 @@ 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..
-- 
2.8.1