printk fixup for 5.16

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Merge tag 'printk-for-5.16-fixup' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

Pull printk fixes from Petr Mladek:

 - Try to flush backtraces from other CPUs also on the local one. This
   was a regression caused by printk_safe buffers removal.

 - Remove header dependency warning.

* tag 'printk-for-5.16-fixup' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
  printk: Remove printk.h inclusion in percpu.h
  printk: restore flushing of NMI buffers on remote CPUs after NMI backtraces

arch/powerpc/kernel/watchdog.c

@@ -187,6 +187,12 @@ static void watchdog_smp_panic(int cpu, u64 tb)
 	if (sysctl_hardlockup_all_cpu_backtrace)
 		trigger_allbutself_cpu_backtrace();
 
+	/*
+	 * Force flush any remote buffers that might be stuck in IRQ context
+	 * and therefore could not run their irq_work.
+	 */
+	printk_trigger_flush();
+
 	if (hardlockup_panic)
 		nmi_panic(NULL, "Hard LOCKUP");
 

include/linux/percpu.h

@@ -6,7 +6,6 @@
 #include <linux/preempt.h>
 #include <linux/smp.h>
 #include <linux/cpumask.h>
-#include <linux/printk.h>
 #include <linux/pfn.h>
 #include <linux/init.h>
 

include/linux/printk.h

@@ -198,6 +198,7 @@ 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;
+void printk_trigger_flush(void);
 #else
 static inline __printf(1, 0)
 int vprintk(const char *s, va_list args)
@@ -274,6 +275,9 @@ static inline void dump_stack_lvl(const char *log_lvl)
 static inline void dump_stack(void)
 {
 }
+static inline void printk_trigger_flush(void)
+{
+}
 #endif
 
 #ifdef CONFIG_SMP

kernel/printk/printk.c

@@ -3253,6 +3253,11 @@ void defer_console_output(void)
 	preempt_enable();
 }
 
+void printk_trigger_flush(void)
+{
+	defer_console_output();
+}
+
 int vprintk_deferred(const char *fmt, va_list args)
 {
 	int r;

lib/nmi_backtrace.c

@@ -75,6 +75,12 @@ void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
 		touch_softlockup_watchdog();
 	}
 
+	/*
+	 * Force flush any remote buffers that might be stuck in IRQ context
+	 * and therefore could not run their irq_work.
+	 */
+	printk_trigger_flush();
+
 	clear_bit_unlock(0, &backtrace_flag);
 	put_cpu();
 }