[RFC][PATCHv2 4/7] printk: make alt_printk available when config printk set

[Sergey Senozhatsky]

alt_printk must be enabled on systems that have CONFIG_PRINTK set,
while NMI related functions must depend on CONFIG_PRINTK_NMI.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
---
 include/linux/printk.h     | 21 +++++++++++++++------
 kernel/printk/Makefile     |  2 +-
 kernel/printk/alt_printk.c | 30 +++++++++++++++++++++++++-----
 3 files changed, 41 insertions(+), 12 deletions(-)

diff --git a/include/linux/printk.h b/include/linux/printk.h
index 7510613..068a124 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -131,17 +131,11 @@ void early_printk(const char *s, ...) { }
 #endif
 
 #ifdef CONFIG_PRINTK_NMI
-extern void alt_printk_init(void);
 extern void printk_nmi_enter(void);
 extern void printk_nmi_exit(void);
-extern void alt_printk_flush(void);
-extern void alt_printk_flush_on_panic(void);
 #else
-static inline void alt_printk_init(void) { }
 static inline void printk_nmi_enter(void) { }
 static inline void printk_nmi_exit(void) { }
-static inline void alt_printk_flush(void) { }
-static inline void alt_printk_flush_on_panic(void) { }
 #endif /* PRINTK_NMI */
 
 #ifdef CONFIG_PRINTK
@@ -193,6 +187,9 @@ void __init setup_log_buf(int early);
 __printf(1, 2) void dump_stack_set_arch_desc(const char *fmt, ...);
 void dump_stack_print_info(const char *log_lvl);
 void show_regs_print_info(const char *log_lvl);
+extern void alt_printk_init(void);
+extern void alt_printk_flush(void);
+extern void alt_printk_flush_on_panic(void);
 #else
 static inline __printf(1, 0)
 int vprintk(const char *s, va_list args)
@@ -252,6 +249,18 @@ static inline void dump_stack_print_info(const char *log_lvl)
 static inline void show_regs_print_info(const char *log_lvl)
 {
 }
+
+static inline void alt_printk_init(void)
+{
+}
+
+static inline void alt_printk_flush(void)
+{
+}
+
+static inline void alt_printk_flush_on_panic(void)
+{
+}
 #endif
 
 extern asmlinkage void dump_stack(void) __cold;
diff --git a/kernel/printk/Makefile b/kernel/printk/Makefile
index 3fc5e4e..d11838c 100644
--- a/kernel/printk/Makefile
+++ b/kernel/printk/Makefile
@@ -1,3 +1,3 @@
 obj-y	= printk.o
-obj-$(CONFIG_PRINTK_NMI)		+= alt_printk.o
+obj-$(CONFIG_PRINTK)		+= alt_printk.o
 obj-$(CONFIG_A11Y_BRAILLE_CONSOLE)	+= braille.o
diff --git a/kernel/printk/alt_printk.c b/kernel/printk/alt_printk.c
index 4bc1e7d..db0bfc8 100644
--- a/kernel/printk/alt_printk.c
+++ b/kernel/printk/alt_printk.c
@@ -40,7 +40,6 @@
  * were handled or when IRQs are blocked.
  */
 static int alt_printk_irq_ready;
-atomic_t nmi_message_lost;
 
 #define ALT_LOG_BUF_LEN ((1 << CONFIG_ALT_PRINTK_LOG_BUF_SHIFT) -	\
 			 sizeof(atomic_t) - sizeof(struct irq_work))
@@ -50,12 +49,16 @@ struct alt_printk_seq_buf {
 	struct irq_work		work;	/* IRQ work that flushes the buffer */
 	unsigned char		buffer[ALT_LOG_BUF_LEN];
 };
-static DEFINE_PER_CPU(struct alt_printk_seq_buf, nmi_print_seq);
 
 static DEFINE_PER_CPU(struct alt_printk_seq_buf, alt_print_seq);
 static DEFINE_PER_CPU(int, alt_printk_ctx);
 static DEFINE_PER_CPU(unsigned long, alt_printk_irq_flags);
 
+#ifdef CONFIG_PRINTK_NMI
+static DEFINE_PER_CPU(struct alt_printk_seq_buf, nmi_print_seq);
+atomic_t nmi_message_lost;
+#endif
+
 static int alt_printk_log_store(struct alt_printk_seq_buf *s,
 		const char *fmt, va_list args)
 {
@@ -204,8 +207,12 @@ void alt_printk_flush(void)
 {
 	int cpu;
 
-	for_each_possible_cpu(cpu)
+	for_each_possible_cpu(cpu) {
+#ifdef CONFIG_PRINTK_NMI
 		__alt_printk_flush(&per_cpu(nmi_print_seq, cpu).work);
+#endif
+		__alt_printk_flush(&per_cpu(alt_print_seq, cpu).work);
+	}
 }
 
 /**
@@ -235,6 +242,8 @@ void alt_printk_flush_on_panic(void)
 	alt_printk_flush();
 }
 
+#ifdef CONFIG_PRINTK_NMI
+
 /*
  * Safe printk() for NMI context. It uses a per-CPU buffer to
  * store the message. NMIs are not nested, so there is always only
@@ -263,6 +272,15 @@ void printk_nmi_exit(void)
 	this_cpu_and(alt_printk_ctx, ~ALT_PRINTK_NMI_CONTEXT_MASK);
 }
 
+#else
+
+static int vprintk_nmi(const char *fmt, va_list args)
+{
+	return 0;
+}
+
+#endif /* CONFIG_PRINTK_NMI */
+
 /*
  * Lockless printk(), to avoid deadlocks should the printk() recurse
  * into itself. It uses a per-CPU buffer to store the message, just like
@@ -317,12 +335,14 @@ void __init alt_printk_init(void)
 	int cpu;
 
 	for_each_possible_cpu(cpu) {
-		struct alt_printk_seq_buf *s = &per_cpu(nmi_print_seq, cpu);
+		struct alt_printk_seq_buf *s = &per_cpu(alt_print_seq, cpu);
 
 		init_irq_work(&s->work, __alt_printk_flush);
 
-		s = &per_cpu(alt_print_seq, cpu);
+#ifdef CONFIG_PRINTK_NMI
+		s = &per_cpu(nmi_print_seq, cpu);
 		init_irq_work(&s->work, __alt_printk_flush);
+#endif
 	}
 
 	/* Make sure that IRQ works are initialized before enabling. */
-- 
2.10.0.372.g6fe1b14