kmsg: make sure all messages reach a newly registered boot console

We suppress printing kmsg records to the console, which are already printed
immediately while we have received their fragments.

Newly registered boot consoles print the entire kmsg buffer during
registration. Clear the console-suppress flag after we skipped the record
during its first storage, so any later print will see these records as usual.
Signed-off-by: NKay Sievers <kay@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

kernel/printk.c

@@ -1953,6 +1953,12 @@ void console_unlock(void)
 			 */
 			console_idx = log_next(console_idx);
 			console_seq++;
+			/*
+			 * We will get here again when we register a new
+			 * CON_PRINTBUFFER console. Clear the flag so we
+			 * will properly dump everything later.
+			 */
+			msg->flags &= ~LOG_NOCONS;
 			goto skip;
 		}