From 292e0056ea51b87d901f765b4c35dd85d5589935 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Tue, 22 Jan 2013 16:48:03 -0800
Subject: [PATCH] --- yaml --- r: 350308 b: refs/heads/master c:
 0fdff3ec6d87856cdcc99e69cf42143fdd6c56b4 h: refs/heads/master v: v3

---
 [refs]              | 2 +-
 trunk/kernel/kmod.c | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 1b805695312b..f32b5ea2539d 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 21c3c5d2800733b7a276725b8e1ae49a694adc1a
+refs/heads/master: 0fdff3ec6d87856cdcc99e69cf42143fdd6c56b4
diff --git a/trunk/kernel/kmod.c b/trunk/kernel/kmod.c
index 1c317e386831..ecd42b484db8 100644
--- a/trunk/kernel/kmod.c
+++ b/trunk/kernel/kmod.c
@@ -38,6 +38,7 @@
 #include <linux/suspend.h>
 #include <linux/rwsem.h>
 #include <linux/ptrace.h>
+#include <linux/async.h>
 #include <asm/uaccess.h>
 
 #include <trace/events/module.h>
@@ -130,6 +131,14 @@ int __request_module(bool wait, const char *fmt, ...)
 #define MAX_KMOD_CONCURRENT 50	/* Completely arbitrary value - KAO */
 	static int kmod_loop_msg;
 
+	/*
+	 * We don't allow synchronous module loading from async.  Module
+	 * init may invoke async_synchronize_full() which will end up
+	 * waiting for this task which already is waiting for the module
+	 * loading to complete, leading to a deadlock.
+	 */
+	WARN_ON_ONCE(wait && current_is_async());
+
 	va_start(args, fmt);
 	ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
 	va_end(args);