linux/debian/patches-rt/0208-kernel-printk-Don-t-try-to-print-from-IRQ-NMI-region.patch

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Thu, 19 May 2016 17:45:27 +0200
Subject: [PATCH 208/290] kernel/printk: Don't try to print from IRQ/NMI region
Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=8c719aa550b2e9bb95786ce26d5fbff438268cbd

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(+)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index c66755a0a046..1935cf91db0c 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1782,6 +1782,11 @@ static void call_console_drivers(const char *ext_text, size_t ext_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)
@@ -2540,6 +2545,11 @@ 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..