From 5a5d7e9badd2cb8065db171961bd30bd3595e4b6 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Thu, 26 Jan 2023 16:08:31 +0100
Subject: cpuidle: lib/bug: Disable rcu_is_watching() during WARN/BUG

In order to avoid WARN/BUG from generating nested or even recursive
warnings, force rcu_is_watching() true during
WARN/lockdep_rcu_suspicious().

Notably things like unwinding the stack can trigger rcu_dereference()
warnings, which then triggers more unwinding which then triggers more
warnings etc..

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230126151323.408156109@infradead.org
---
 kernel/locking/lockdep.c | 3 +++
 kernel/panic.c           | 5 +++++
 2 files changed, 8 insertions(+)

(limited to 'kernel')

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index e3375bc40dad..50d4863974e7 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -55,6 +55,7 @@
 #include <linux/rcupdate.h>
 #include <linux/kprobes.h>
 #include <linux/lockdep.h>
+#include <linux/context_tracking.h>
 
 #include <asm/sections.h>
 
@@ -6555,6 +6556,7 @@ void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
 {
 	struct task_struct *curr = current;
 	int dl = READ_ONCE(debug_locks);
+	bool rcu = warn_rcu_enter();
 
 	/* Note: the following can be executed concurrently, so be careful. */
 	pr_warn("\n");
@@ -6595,5 +6597,6 @@ void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
 	lockdep_print_held_locks(curr);
 	pr_warn("\nstack backtrace:\n");
 	dump_stack();
+	warn_rcu_exit(rcu);
 }
 EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);
diff --git a/kernel/panic.c b/kernel/panic.c
index 463c9295bc28..487f5b03bf83 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -34,6 +34,7 @@
 #include <linux/ratelimit.h>
 #include <linux/debugfs.h>
 #include <linux/sysfs.h>
+#include <linux/context_tracking.h>
 #include <trace/events/error_report.h>
 #include <asm/sections.h>
 
@@ -679,6 +680,7 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
 void warn_slowpath_fmt(const char *file, int line, unsigned taint,
 		       const char *fmt, ...)
 {
+	bool rcu = warn_rcu_enter();
 	struct warn_args args;
 
 	pr_warn(CUT_HERE);
@@ -693,11 +695,13 @@ void warn_slowpath_fmt(const char *file, int line, unsigned taint,
 	va_start(args.args, fmt);
 	__warn(file, line, __builtin_return_address(0), taint, NULL, &args);
 	va_end(args.args);
+	warn_rcu_exit(rcu);
 }
 EXPORT_SYMBOL(warn_slowpath_fmt);
 #else
 void __warn_printk(const char *fmt, ...)
 {
+	bool rcu = warn_rcu_enter();
 	va_list args;
 
 	pr_warn(CUT_HERE);
@@ -705,6 +709,7 @@ void __warn_printk(const char *fmt, ...)
 	va_start(args, fmt);
 	vprintk(fmt, args);
 	va_end(args);
+	warn_rcu_exit(rcu);
 }
 EXPORT_SYMBOL(__warn_printk);
 #endif
-- 
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