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Subject[PATCH RT 15/20] kernel/printk: Dont try to print from IRQ/NMI region
4.1.27-rt31-rc1 stable review patch.
If anyone has any objections, please let me know.

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

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

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 899645a2ebcc..398bf2bbd3bc 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1426,6 +1426,11 @@ 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)
@@ -2392,6 +2397,11 @@ 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

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