Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/um/kernel/sigio.c b/arch/um/kernel/sigio.c
index b5e0cbb..10c99e0 100644
--- a/arch/um/kernel/sigio.c
+++ b/arch/um/kernel/sigio.c
@@ -1,6 +1,6 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
- * Licensed under the GPL
  */
 
 #include <linux/interrupt.h>
@@ -16,7 +16,6 @@
 	char c;
 
 	os_read_file(sigio_irq_fd, &c, sizeof(c));
-	reactivate_fd(sigio_irq_fd, SIGIO_WRITE_IRQ);
 	return IRQ_HANDLED;
 }