From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 17 Nov 2016 16:31:55 +0000 (+0100)
Subject: kernel/printk: Block cpuhotplug callback when tasks are frozen
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=f97960fbddd98e1b7bfba469b8510b49a62b4bc5;p=linux-beck.git

kernel/printk: Block cpuhotplug callback when tasks are frozen

The recent conversion of the console hotplug notifier to the state machine
missed the fact, that the notifier only operated on the non frozen
transitions. As a consequence the console_lock/unlock() pair is also
invoked during suspend, which results in a lockdep warning.

Restore the previous state by making the lock/unlock conditional on
!tasks_frozen.

Fixes: 90b14889d2f9 ("kernel/printk: Convert to hotplug state machine")
Reported-and-tested-by: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1611171729320.3645@nanos
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 4487ffcd42d5..37893da9bae8 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2194,8 +2194,10 @@ void resume_console(void)
  */
 static int console_cpu_notify(unsigned int cpu)
 {
-	console_lock();
-	console_unlock();
+	if (!cpuhp_tasks_frozen) {
+		console_lock();
+		console_unlock();
+	}
 	return 0;
 }