Avoid kernel hang reading /sys/hypervisor/uuid if xenstore is not available.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>

diff --git a/drivers/xen/core/xen_sysfs.c b/drivers/xen/core/xen_sysfs.c
index d7e188b6197ad5d0159d4a63a9eeb8e5657fcbf6..745c84b7a27d0317e15f16450286e65b010b58f5 100644 (file)
--- a/drivers/xen/core/xen_sysfs.c
+++ b/drivers/xen/core/xen_sysfs.c
@@ -104,6 +104,10 @@ static ssize_t uuid_show(struct hyp_sysfs_attr *attr, char *buffer)
 {
        char *vm, *val;
        int ret;
+       extern int xenstored_ready;
+
+       if (!xenstored_ready)
+               return -EBUSY;
 
        vm = xenbus_read(XBT_NIL, "vm", "", NULL);
        if (IS_ERR(vm))