Merge tag 'printk-for-5.8-kdb-nmi' of git://git.kernel.org/pub/scm/li…

…nux/kernel/git/printk/linux

Pull printk fix from Petr Mladek:
 "One more printk change for 5.8: make sure that messages printed from
  KDB context are redirected to KDB console handlers. It did not work
  when KDB interrupted NMI or printk_safe contexts.

  Arm people started hitting this problem more often recently. I forgot
  to add the fix into the previous pull request by mistake"

* tag 'printk-for-5.8-kdb-nmi' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
  printk/kdb: Redirect printk messages into kdb in any context

kernel/printk/printk.c

@@ -35,7 +35,6 @@
 #include <linux/memblock.h>
 #include <linux/syscalls.h>
 #include <linux/crash_core.h>
-#include <linux/kdb.h>
 #include <linux/ratelimit.h>
 #include <linux/kmsg_dump.h>
 #include <linux/syslog.h>
@@ -2047,18 +2046,7 @@ EXPORT_SYMBOL(vprintk);
 
 int vprintk_default(const char *fmt, va_list args)
 {
-	int r;
-
-#ifdef CONFIG_KGDB_KDB
-	/* Allow to pass printk() to kdb but avoid a recursion. */
-	if (unlikely(kdb_trap_printk && kdb_printf_cpu < 0)) {
-		r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
-		return r;
-	}
-#endif
-	r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
-
-	return r;
+	return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
 }
 EXPORT_SYMBOL_GPL(vprintk_default);
 

kernel/printk/printk_safe.c

@@ -6,6 +6,7 @@
 #include <linux/preempt.h>
 #include <linux/spinlock.h>
 #include <linux/debug_locks.h>
+#include <linux/kdb.h>
 #include <linux/smp.h>
 #include <linux/cpumask.h>
 #include <linux/irq_work.h>
@@ -360,6 +361,12 @@ void __printk_safe_exit(void)
 
 __printf(1, 0) int vprintk_func(const char *fmt, va_list args)
 {
+#ifdef CONFIG_KGDB_KDB
+	/* Allow to pass printk() to kdb but avoid a recursion. */
+	if (unlikely(kdb_trap_printk && kdb_printf_cpu < 0))
+		return vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
+#endif
+
 	/*
 	 * Try to use the main logbuf even in NMI. But avoid calling console
 	 * drivers that might have their own locks.