linux-kernel - [PATCH printk v2 25/26] rcu: Mark emergency section in rcu stalls

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Date: Sun, 18 Feb 2024 20:03:25 +0106
From: John Ogness <john.ogness@...utronix.de>
To: Petr Mladek <pmladek@...e.com>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	Neeraj Upadhyay <quic_neeraju@...cinc.com>,
	Joel Fernandes <joel@...lfernandes.org>,
	Josh Triplett <josh@...htriplett.org>,
	Boqun Feng <boqun.feng@...il.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>,
	rcu@...r.kernel.org
Subject: [PATCH printk v2 25/26] rcu: Mark emergency section in rcu stalls

Mark an emergency section within print_other_cpu_stall(), where
RCU stall information is printed. In this section, the CPU will
not perform console output for the printk() calls. Instead, a
flushing of the console output is triggered when exiting the
emergency section.

Signed-off-by: John Ogness <john.ogness@...utronix.de>
---
 kernel/rcu/tree_stall.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index ac8e86babe44..efb2be8939a2 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -9,6 +9,7 @@
 
 #include <linux/kvm_para.h>
 #include <linux/rcu_notifier.h>
+#include <linux/console.h>
 
 //////////////////////////////////////////////////////////////////////////////
 //
@@ -604,6 +605,8 @@ static void print_other_cpu_stall(unsigned long gp_seq, unsigned long gps)
 	if (rcu_stall_is_suppressed())
 		return;
 
+	nbcon_cpu_emergency_enter();
+
 	/*
 	 * OK, time to rat on our buddy...
 	 * See Documentation/RCU/stallwarn.rst for info on how to debug
@@ -658,6 +661,8 @@ static void print_other_cpu_stall(unsigned long gp_seq, unsigned long gps)
 	panic_on_rcu_stall();
 
 	rcu_force_quiescent_state();  /* Kick them all. */
+
+	nbcon_cpu_emergency_exit();
 }
 
 static void print_cpu_stall(unsigned long gps)
-- 
2.39.2