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From: John Ogness <john.ogness@linutronix.de>
Date: Mon, 11 Sep 2023 15:53:39 +0000
Subject: [PATCH 31/48] rcu: Mark emergency sections in rcu stalls
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.8/older/patches-6.8.2-rt11.tar.xz
Mark emergency sections wherever multiple lines of
rcu stall information are generated. In an emergency
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.
This allows the full message block to be stored as
quickly as possible in the ringbuffer.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
kernel/rcu/tree_exp.h | 7 +++++++
kernel/rcu/tree_stall.h | 9 +++++++++
2 files changed, 16 insertions(+)
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -7,6 +7,7 @@
* Authors: Paul E. McKenney <paulmck@linux.ibm.com>
*/
+#include <linux/console.h>
#include <linux/lockdep.h>
static void rcu_exp_handler(void *unused);
@@ -636,6 +637,9 @@ static void synchronize_rcu_expedited_wa
return;
if (rcu_stall_is_suppressed())
continue;
+
+ nbcon_cpu_emergency_enter();
+
j = jiffies;
rcu_stall_notifier_call_chain(RCU_STALL_NOTIFY_EXP, (void *)(j - jiffies_start));
trace_rcu_stall_warning(rcu_state.name, TPS("ExpeditedStall"));
@@ -689,6 +693,9 @@ static void synchronize_rcu_expedited_wa
rcu_exp_print_detail_task_stall_rnp(rnp);
}
jiffies_stall = 3 * rcu_exp_jiffies_till_stall_check() + 3;
+
+ nbcon_cpu_emergency_exit();
+
panic_on_rcu_stall();
}
}
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -7,6 +7,7 @@
* Author: Paul E. McKenney <paulmck@linux.ibm.com>
*/
+#include <linux/console.h>
#include <linux/kvm_para.h>
#include <linux/rcu_notifier.h>
@@ -604,6 +605,8 @@ static void print_other_cpu_stall(unsign
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
@@ -655,6 +658,8 @@ static void print_other_cpu_stall(unsign
rcu_check_gp_kthread_expired_fqs_timer();
rcu_check_gp_kthread_starvation();
+ nbcon_cpu_emergency_exit();
+
panic_on_rcu_stall();
rcu_force_quiescent_state(); /* Kick them all. */
@@ -675,6 +680,8 @@ static void print_cpu_stall(unsigned lon
if (rcu_stall_is_suppressed())
return;
+ nbcon_cpu_emergency_enter();
+
/*
* OK, time to rat on ourselves...
* See Documentation/RCU/stallwarn.rst for info on how to debug
@@ -703,6 +710,8 @@ static void print_cpu_stall(unsigned lon
jiffies + 3 * rcu_jiffies_till_stall_check() + 3);
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+ nbcon_cpu_emergency_exit();
+
panic_on_rcu_stall();
/*
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