[PATCH printk v2 07/26] printk: Check printk_deferred_enter()/_exit() usage

[John Ogness <john.ogness@linutronix.de>]

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

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

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
---
 include/linux/printk.h      |  7 +++++--
 kernel/printk/printk_safe.c | 12 ++++++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/include/linux/printk.h b/include/linux/printk.h
index 955e31860095..8d5c5588eec9 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -159,13 +159,16 @@ __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
diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
index 6d10927a07d8..8d9408d653de 100644
--- a/kernel/printk/printk_safe.c
+++ b/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();
+	this_cpu_inc(printk_context);
+}
+
+void __printk_deferred_exit(void)
+{
+	cant_migrate();
+	this_cpu_dec(printk_context);
+}
+
 asmlinkage int vprintk(const char *fmt, va_list args)
 {
 #ifdef CONFIG_KGDB_KDB
-- 
2.39.2