[PATCH v2 2/8] Add workaround for xenstore-control flood issues

[Edwin Török <edvin.torok@xxxxxxxxxx>]

There are alternative fixes for this, e.g. do the entire live update
inside oxenstored and reply OK from the next oxenstored or an error.
This requires some asynchronous handling there.

Once that code is available we can revert this one.

Signed-off-by: Edwin Török <edvin.torok@xxxxxxxxxx>
Reviewed-by: Pau Ruiz Safont <pau.safont@xxxxxxxxxx>
Reviewed-by: Christian Lindig <christian.lindig@xxxxxxxxxx>
---
Changed since V1:
* post publicly now that the XSA is out
---
 tools/xenstore/xenstore_control.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/tools/xenstore/xenstore_control.c 
b/tools/xenstore/xenstore_control.c
index 5ca015a07d..611e8b4fdd 100644
--- a/tools/xenstore/xenstore_control.c
+++ b/tools/xenstore/xenstore_control.c
@@ -42,6 +42,10 @@ static int live_update_start(struct xs_handle *xsh, bool 
force, unsigned int to)
         len = add_to_buf(&buf, "-F", len);
     if (len < 0)
         return 1;
+    /* +1 for rounding issues
+     * +1 to give oxenstored a chance to timeout and report back first
+     */
+    to += 2;
 
     for (time_start = time(NULL); time(NULL) - time_start < to;) {
         ret = xs_control_command(xsh, "live-update", buf, len);
@@ -49,6 +53,15 @@ static int live_update_start(struct xs_handle *xsh, bool 
force, unsigned int to)
             goto err;
         if (strcmp(ret, "BUSY"))
             break;
+        /* TODO: use task ID for commands, avoid busy loop polling
+here
+         * oxenstored checks BUSY condition internally on every main
+loop iteration anyway.
+         * Avoid flooding xenstored with live-update requests.
+         * The flooding can also cause the evtchn to overflow in
+xenstored which makes
+         * xenstored enter an infinite loop */
+        sleep(1);
     }
 
     if (strcmp(ret, "OK"))
-- 
2.29.2