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 <[email protected]> Reviewed-by: Petr Mladek <[email protected]> Signed-off-by: Petr Mladek <[email protected]> Link: https://lore.kernel.org/r/[email protected]
torvalds · Jul 26, 2021 · 93d102f · 93d102f
1 parent 002eb6a
commit 93d102f
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Showing 9 changed files with 48 additions and 450 deletions.
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
@@ -170,7 +170,6 @@ extern void panic_flush_kmsg_start(void)
 
 extern void panic_flush_kmsg_end(void)
 {
-	printk_safe_flush_on_panic();
 	kmsg_dump(KMSG_DUMP_PANIC);
 	bust_spinlocks(0);
 	debug_locks_off();

diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c
@@ -183,11 +183,6 @@ static void watchdog_smp_panic(int cpu, u64 tb)
 
 	wd_smp_unlock(&flags);
 
-	printk_safe_flush();
-	/*
-	 * printk_safe_flush() seems to require another print
-	 * before anything actually goes out to console.
-	 */
 	if (sysctl_hardlockup_all_cpu_backtrace)
 		trigger_allbutself_cpu_backtrace();
 

diff --git 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

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
@@ -978,7 +978,6 @@ void crash_kexec(struct pt_regs *regs)
 	old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, this_cpu);
 	if (old_cpu == PANIC_CPU_INVALID) {
 		/* This is the 1st CPU which comes here, so go ahead. */
-		printk_safe_flush_on_panic();
 		__crash_kexec(regs);
 
 		/*

diff --git a/kernel/panic.c b/kernel/panic.c
@@ -247,7 +247,6 @@ void panic(const char *fmt, ...)
 	 * Bypass the panic_cpu check and call __crash_kexec directly.
 	 */
 	if (!_crash_kexec_post_notifiers) {
-		printk_safe_flush_on_panic();
 		__crash_kexec(NULL);
 
 		/*
@@ -271,8 +270,6 @@ void panic(const char *fmt, ...)
 	 */
 	atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
 
-	/* Call flush even twice. It tries harder with a single online CPU */
-	printk_safe_flush_on_panic();
 	kmsg_dump(KMSG_DUMP_PANIC);
 
 	/*

diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
@@ -22,7 +22,6 @@ __printf(1, 0) int vprintk_deferred(const char *fmt, va_list args);
 void __printk_safe_enter(void);
 void __printk_safe_exit(void);
 
-void printk_safe_init(void);
 bool printk_percpu_data_ready(void);
 
 #define printk_safe_enter_irqsave(flags)	\
@@ -37,18 +36,6 @@ bool printk_percpu_data_ready(void);
 		local_irq_restore(flags);	\
 	} while (0)
 
-#define printk_safe_enter_irq()		\
-	do {					\
-		local_irq_disable();		\
-		__printk_safe_enter();		\
-	} while (0)
-
-#define printk_safe_exit_irq()			\
-	do {					\
-		__printk_safe_exit();		\
-		local_irq_enable();		\
-	} while (0)
-
 void defer_console_output(void);
 
 #else
@@ -61,9 +48,5 @@ void defer_console_output(void);
 #define printk_safe_enter_irqsave(flags) local_irq_save(flags)
 #define printk_safe_exit_irqrestore(flags) local_irq_restore(flags)
 
-#define printk_safe_enter_irq() local_irq_disable()
-#define printk_safe_exit_irq() local_irq_enable()
-
-static inline void printk_safe_init(void) { }
 static inline bool printk_percpu_data_ready(void) { return false; }
 #endif /* CONFIG_PRINTK */