xen/xenbus: Avoid synchronous wait on XenBus stalling shutdown/restart.

[cascardo/linux.git] / drivers / xen / xenbus / xenbus_xs.c

diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c
index b6d5fff..ba804f3 100644 (file)
--- a/drivers/xen/xenbus/xenbus_xs.c
+++ b/drivers/xen/xenbus/xenbus_xs.c
@@ -50,6 +50,7 @@
 #include <xen/xenbus.h>
 #include <xen/xen.h>
 #include "xenbus_comms.h"
+#include "xenbus_probe.h"
 
 struct xs_stored_msg {
        struct list_head list;
@@ -139,6 +140,29 @@ static int get_error(const char *errorstring)
        return xsd_errors[i].errnum;
 }
 
+static bool xenbus_ok(void)
+{
+       switch (xen_store_domain_type) {
+       case XS_LOCAL:
+               switch (system_state) {
+               case SYSTEM_POWER_OFF:
+               case SYSTEM_RESTART:
+               case SYSTEM_HALT:
+                       return false;
+               default:
+                       break;
+               }
+               return true;
+       case XS_PV:
+       case XS_HVM:
+               /* FIXME: Could check that the remote domain is alive,
+                * but it is normally initial domain. */
+               return true;
+       default:
+               break;
+       }
+       return false;
+}
 static void *read_reply(enum xsd_sockmsg_type *type, unsigned int *len)
 {
        struct xs_stored_msg *msg;
@@ -148,9 +172,20 @@ static void *read_reply(enum xsd_sockmsg_type *type, unsigned int *len)
 
        while (list_empty(&xs_state.reply_list)) {
                spin_unlock(&xs_state.reply_lock);
-               /* XXX FIXME: Avoid synchronous wait for response here. */
-               wait_event(xs_state.reply_waitq,
-                          !list_empty(&xs_state.reply_list));
+               if (xenbus_ok())
+                       /* XXX FIXME: Avoid synchronous wait for response here. */
+                       wait_event_timeout(xs_state.reply_waitq,
+                                          !list_empty(&xs_state.reply_list),
+                                          msecs_to_jiffies(500));
+               else {
+                       /*
+                        * If we are in the process of being shut-down there is
+                        * no point of trying to contact XenBus - it is either
+                        * killed (xenstored application) or the other domain
+                        * has been killed or is unreachable.
+                        */
+                       return ERR_PTR(-EIO);
+               }
                spin_lock(&xs_state.reply_lock);
        }
 
@@ -215,6 +250,9 @@ void *xenbus_dev_request_and_reply(struct xsd_sockmsg *msg)
 
        mutex_unlock(&xs_state.request_mutex);
 
+       if (IS_ERR(ret))
+               return ret;
+
        if ((msg->type == XS_TRANSACTION_END) ||
            ((req_msg.type == XS_TRANSACTION_START) &&
             (msg->type == XS_ERROR)))