Subject: [PATCH 09/48] printk: Check printk_deferred_enter()/_exit() usage
From: Sebastian Andrzej Siewior <[email-masked]>
Date: Fri, 22 Sep 2023 14:58:18 +0000

Add validation that printk_deferred_enter()/_exit() are called in
non-migration contexts.

Signed-off-by: Sebastian Andrzej Siewior <[email-masked]>
Signed-off-by: John Ogness <[email-masked]>
Reviewed-by: Petr Mladek <[email-masked]>
Signed-off-by: Sebastian Andrzej Siewior <[email-masked]>
---
 include/linux/printk.h      |    9 +++++----
 kernel/printk/internal.h    |    3 +++
 kernel/printk/printk_safe.c |   12 ++++++++++++
 3 files changed, 20 insertions(+), 4 deletions(-)

Index: linux-6.8.2-rt10/include/linux/printk.h
===================================================================
--- linux-6.8.2-rt10.orig/include/linux/printk.h
+++ linux-6.8.2-rt10/include/linux/printk.h
@@ -157,15 +157,16 @@ int _printk(const char *fmt, ...);
  */
 __printf(1, 2) __cold int _printk_deferred(const char *fmt, ...);
 
-extern void __printk_safe_enter(void);
-extern void __printk_safe_exit(void);
+extern void __printk_deferred_enter(void);
+extern void __printk_deferred_exit(void);
+
 /*
  * The printk_deferred_enter/exit macros are available only as a hack for
  * some code paths that need to defer all printk console printing. Interrupts
  * must be disabled for the deferred duration.
  */
-#define printk_deferred_enter __printk_safe_enter
-#define printk_deferred_exit __printk_safe_exit
+#define printk_deferred_enter() __printk_deferred_enter()
+#define printk_deferred_exit() __printk_deferred_exit()
 
 /*
  * Please don't use printk_ratelimit(), because it shares ratelimiting state
Index: linux-6.8.2-rt10/kernel/printk/internal.h
===================================================================
--- linux-6.8.2-rt10.orig/kernel/printk/internal.h
+++ linux-6.8.2-rt10/kernel/printk/internal.h
@@ -53,6 +53,9 @@ int vprintk_store(int facility, int leve
 __printf(1, 0) int vprintk_default(const char *fmt, va_list args);
 __printf(1, 0) int vprintk_deferred(const char *fmt, va_list args);
 
+void __printk_safe_enter(void);
+void __printk_safe_exit(void);
+
 bool printk_percpu_data_ready(void);
 
 #define printk_safe_enter_irqsave(flags)	\
Index: linux-6.8.2-rt10/kernel/printk/printk_safe.c
===================================================================
--- linux-6.8.2-rt10.orig/kernel/printk/printk_safe.c
+++ linux-6.8.2-rt10/kernel/printk/printk_safe.c
@@ -26,6 +26,18 @@ void __printk_safe_exit(void)
 	this_cpu_dec(printk_context);
 }
 
+void __printk_deferred_enter(void)
+{
+	cant_migrate();
+	__printk_safe_enter();
+}
+
+void __printk_deferred_exit(void)
+{
+	cant_migrate();
+	__printk_safe_exit();
+}
+
 asmlinkage int vprintk(const char *fmt, va_list args)
 {
 #ifdef CONFIG_KGDB_KDB