1 files changed, 46 insertions, 9 deletions

diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
index 6d10927a07d8..32a28f563b13 100644
--- a/kernel/printk/printk_safe.c
+++ b/kernel/printk/printk_safe.c
@@ -12,6 +12,24 @@
 
 #include "internal.h"
 
+/* Context where printk messages are never suppressed */
+static atomic_t force_con;
+
+void printk_force_console_enter(void)
+{
+	atomic_inc(&force_con);
+}
+
+void printk_force_console_exit(void)
+{
+	atomic_dec(&force_con);
+}
+
+bool is_printk_force_console(void)
+{
+	return atomic_read(&force_con);
+}
+
 static DEFINE_PER_CPU(int, printk_context);
 
 /* Can be preempted by NMI. */
@@ -26,6 +44,34 @@ void __printk_safe_exit(void)
 	this_cpu_dec(printk_context);
 }
 
+void __printk_deferred_enter(void)
+{
+	cant_migrate();
+	__printk_safe_enter();
+}
+
+void __printk_deferred_exit(void)
+{
+	cant_migrate();
+	__printk_safe_exit();
+}
+
+bool is_printk_legacy_deferred(void)
+{
+	/*
+	 * The per-CPU variable @printk_context can be read safely in any
+	 * context. CPU migration is always disabled when set.
+	 *
+	 * A context holding the printk_cpu_sync must not spin waiting for
+	 * another CPU. For legacy printing, it could be the console_lock
+	 * or the port lock.
+	 */
+	return (force_legacy_kthread() ||
+		this_cpu_read(printk_context) ||
+		in_nmi() ||
+		is_printk_cpu_sync_owner());
+}
+
 asmlinkage int vprintk(const char *fmt, va_list args)
 {
 #ifdef CONFIG_KGDB_KDB
@@ -33,15 +79,6 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 	if (unlikely(kdb_trap_printk && kdb_printf_cpu < 0))
 		return vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
 #endif
-
-	/*
-	 * Use the main logbuf even in NMI. But avoid calling console
-	 * drivers that might have their own locks.
-	 */
-	if (this_cpu_read(printk_context) || in_nmi())
-		return vprintk_deferred(fmt, args);
-
-	/* No obstacles. */
 	return vprintk_default(fmt, args);
 }
 EXPORT_SYMBOL(vprintk);