From 41716b8d5151d2bec72b6796ed58b6206cdb4779 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= <royger@FreeBSD.org>
Date: Tue, 7 Mar 2017 09:17:48 +0000
Subject: [PATCH] xenstore: fix suspension when using the xenstore device

Lock the xenstore request mutex when suspending user-space processes, in order
to prevent any process from holding this lock when going into suspension, or
else the xenstore suspend process is going to deadlock.

Submitted by:		Liuyingdong <liuyingdong@huawei.com>
Reviewed by:		royger
MFC after:		2 weeks
Differential revision:	https://reviews.freebsd.org/D9638
---
 sys/dev/xen/control/control.c   |  2 ++
 sys/dev/xen/xenstore/xenstore.c | 17 +++++++++++++++++
 sys/xen/xenstore/xenstorevar.h  | 11 +++++++++++
 3 files changed, 30 insertions(+)

diff --git a/sys/dev/xen/control/control.c b/sys/dev/xen/control/control.c
index d4249886332b..d5aa97e03b73 100644
--- a/sys/dev/xen/control/control.c
+++ b/sys/dev/xen/control/control.c
@@ -199,7 +199,9 @@ xctrl_suspend()
 #endif
 
 	EVENTHANDLER_INVOKE(power_suspend_early);
+	xs_lock();
 	stop_all_proc();
+	xs_unlock();
 	EVENTHANDLER_INVOKE(power_suspend);
 
 #ifdef EARLY_AP_STARTUP
diff --git a/sys/dev/xen/xenstore/xenstore.c b/sys/dev/xen/xenstore/xenstore.c
index 4f89b7457d0e..9289adfc1a79 100644
--- a/sys/dev/xen/xenstore/xenstore.c
+++ b/sys/dev/xen/xenstore/xenstore.c
@@ -1699,3 +1699,20 @@ xs_unregister_watch(struct xs_watch *watch)
 		sx_xunlock(&xs.xenwatch_mutex);
 	}
 }
+
+void
+xs_lock(void)
+{
+
+	sx_xlock(&xs.request_mutex);
+	return;
+}
+
+void
+xs_unlock(void)
+{
+
+	sx_xunlock(&xs.request_mutex);
+	return;
+}
+
diff --git a/sys/xen/xenstore/xenstorevar.h b/sys/xen/xenstore/xenstorevar.h
index 208e5bf09b8e..4c612b4b6881 100644
--- a/sys/xen/xenstore/xenstorevar.h
+++ b/sys/xen/xenstore/xenstorevar.h
@@ -338,4 +338,15 @@ void xs_unregister_watch(struct xs_watch *watch);
  */
 struct sbuf *xs_join(const char *, const char *);
 
+/**
+ * Lock the xenstore request mutex.
+ */
+void xs_lock(void);
+
+/**
+ * Unlock the xenstore request mutex.
+ */
+void xs_unlock(void);
+
 #endif /* _XEN_XENSTORE_XENSTOREVAR_H */
+