[Xen-devel] [PATCH V3 2/2] xenbus: delay xenbus frontend resume is xenstored is not running

[Aurelien Chartier <aurelien.chartier@xxxxxxxxxx>]

If the xenbus frontend is located in a domain running xenstored, the device
resume is hanging because it is happening before the process resume. This
patch adds extra logic to the resume code to check if we are the domain
running xenstored and delay the resume if needed.

Signed-off-by: Aurelien Chartier <aurelien.chartier@xxxxxxxxxx>
---
 drivers/xen/xenbus/xenbus_probe_frontend.c |   26 +++++++++++++++++++++++++-
 include/xen/xenbus.h                       |    1 +
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/xenbus/xenbus_probe_frontend.c 
b/drivers/xen/xenbus/xenbus_probe_frontend.c
index 3159a37..217b9c1 100644
--- a/drivers/xen/xenbus/xenbus_probe_frontend.c
+++ b/drivers/xen/xenbus/xenbus_probe_frontend.c
@@ -89,9 +89,33 @@ static void backend_changed(struct xenbus_watch *watch,
        xenbus_otherend_changed(watch, vec, len, 1);
 }
 
+static void xenbus_frontend_delayed_resume(struct work_struct *w)
+{
+       struct xenbus_device *xdev = container_of(w, struct xenbus_device, 
work);
+
+       xenbus_dev_resume(&xdev->dev);
+}
+
+static int xenbus_frontend_dev_resume(struct device *dev)
+{
+       /* 
+        * If xenstored is running in that domain, we cannot access the backend
+        * state at the moment, so we need to defer xenbus_dev_resume
+        */
+       if (xen_store_domain == XS_LOCAL) {
+               struct xenbus_device *xdev = to_xenbus_device(dev);
+
+               INIT_WORK(&xdev->work, xenbus_frontend_delayed_resume);
+               schedule_work(&xdev->work);
+
+               return 0;
+       }
+
+       return xenbus_dev_resume(dev);
+}
 static const struct dev_pm_ops xenbus_pm_ops = {
        .suspend        = xenbus_dev_suspend,
-       .resume         = xenbus_dev_resume,
+       .resume         = xenbus_frontend_dev_resume,
        .freeze         = xenbus_dev_suspend,
        .thaw           = xenbus_dev_cancel,
        .restore        = xenbus_dev_resume,
diff --git a/include/xen/xenbus.h b/include/xen/xenbus.h
index 0a7515c..569c07f 100644
--- a/include/xen/xenbus.h
+++ b/include/xen/xenbus.h
@@ -70,6 +70,7 @@ struct xenbus_device {
        struct device dev;
        enum xenbus_state state;
        struct completion down;
+       struct work_struct work;
 };
 
 static inline struct xenbus_device *to_xenbus_device(struct device *dev)
-- 
1.7.10.4


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