From 93d102f094be9beab28e5afb656c188b16a3793b Mon Sep 17 00:00:00 2001 From: John Ogness Date: Thu, 15 Jul 2021 21:39:56 +0206 Subject: printk: remove safe buffers With @logbuf_lock removed, the high level printk functions for storing messages are lockless. Messages can be stored from any context, so there is no need for the NMI and safe buffers anymore. Remove the NMI and safe buffers. Although the safe buffers are removed, the NMI and safe context tracking is still in place. In these contexts, store the message immediately but still use irq_work to defer the console printing. Since printk recursion tracking is in place, safe context tracking for most of printk is not needed. Remove it. Only safe context tracking relating to the console and console_owner locks is left in place. This is because the console and console_owner locks are needed for the actual printing. Signed-off-by: John Ogness Reviewed-by: Petr Mladek Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20210715193359.25946-4-john.ogness@linutronix.de --- include/linux/printk.h | 10 ---------- 1 file changed, 10 deletions(-) (limited to 'include/linux/printk.h') diff --git a/include/linux/printk.h b/include/linux/printk.h index d796183f26c9..719d919f9b67 100644 --- a/include/linux/printk.h +++ b/include/linux/printk.h @@ -208,8 +208,6 @@ void dump_stack_print_info(const char *log_lvl); void show_regs_print_info(const char *log_lvl); extern asmlinkage void dump_stack_lvl(const char *log_lvl) __cold; extern asmlinkage void dump_stack(void) __cold; -extern void printk_safe_flush(void); -extern void printk_safe_flush_on_panic(void); #else static inline __printf(1, 0) int vprintk(const char *s, va_list args) @@ -277,14 +275,6 @@ static inline void dump_stack_lvl(const char *log_lvl) static inline void dump_stack(void) { } - -static inline void printk_safe_flush(void) -{ -} - -static inline void printk_safe_flush_on_panic(void) -{ -} #endif #ifdef CONFIG_SMP -- cgit v1.2.3 From 85e3e7fbbb720b9897fba9a99659e31cbd1c082e Mon Sep 17 00:00:00 2001 From: John Ogness Date: Thu, 15 Jul 2021 21:39:57 +0206 Subject: printk: remove NMI tracking All NMI contexts are handled the same as the safe context: store the message and defer printing. There is no need to have special NMI context tracking for this. Using in_nmi() is enough. There are several parts of the kernel that are manually calling into the printk NMI context tracking in order to cause general printk deferred printing: arch/arm/kernel/smp.c arch/powerpc/kexec/crash.c kernel/trace/trace.c For arm/kernel/smp.c and powerpc/kexec/crash.c, provide a new function pair printk_deferred_enter/exit that explicitly achieves the same objective. For ftrace, remove the printk context manipulation completely. It was added in commit 03fc7f9c99c1 ("printk/nmi: Prevent deadlock when accessing the main log buffer in NMI"). The purpose was to enforce storing messages directly into the ring buffer even in NMI context. It really should have only modified the behavior in NMI context. There is no need for a special behavior any longer. All messages are always stored directly now. The console deferring is handled transparently in vprintk(). Signed-off-by: John Ogness [pmladek@suse.com: Remove special handling in ftrace.c completely. Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20210715193359.25946-5-john.ogness@linutronix.de --- include/linux/printk.h | 31 +++++++++++++++++++------------ 1 file changed, 19 insertions(+), 12 deletions(-) (limited to 'include/linux/printk.h') diff --git a/include/linux/printk.h b/include/linux/printk.h index 719d919f9b67..a1379df43251 100644 --- a/include/linux/printk.h +++ b/include/linux/printk.h @@ -149,18 +149,6 @@ static inline __printf(1, 2) __cold void early_printk(const char *s, ...) { } #endif -#ifdef CONFIG_PRINTK_NMI -extern void printk_nmi_enter(void); -extern void printk_nmi_exit(void); -extern void printk_nmi_direct_enter(void); -extern void printk_nmi_direct_exit(void); -#else -static inline void printk_nmi_enter(void) { } -static inline void printk_nmi_exit(void) { } -static inline void printk_nmi_direct_enter(void) { } -static inline void printk_nmi_direct_exit(void) { } -#endif /* PRINTK_NMI */ - struct dev_printk_info; #ifdef CONFIG_PRINTK @@ -180,6 +168,16 @@ 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); +/* + * 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 + /* * Please don't use printk_ratelimit(), because it shares ratelimiting state * with all other unrelated printk_ratelimit() callsites. Instead use @@ -224,6 +222,15 @@ int printk_deferred(const char *s, ...) { return 0; } + +static inline void printk_deferred_enter(void) +{ +} + +static inline void printk_deferred_exit(void) +{ +} + static inline int printk_ratelimit(void) { return 0; -- cgit v1.2.3