Mailing List Archive

# HG changeset patch
# User emellor@ewan
# Node ID 00a324b3a2db17545065176a7acf83f45e259ab3
# Parent 09447f91ab4918d40b6a2357b1b8665ffa4726e6
Ignore any watches that fire for which we do not have a registration. This can
happen if there are watches in flight at the same time as a deregistration, and
also seems to happen spuriously on xend restart.

This fixes the Invalid token error that has been seen on xend restart.

Signed-off-by: Ewan Mellor <ewan@xensource.com>

diff -r 09447f91ab49 -r 00a324b3a2db tools/python/xen/lowlevel/xs/xs.c
--- a/tools/python/xen/lowlevel/xs/xs.c Wed Oct 12 11:56:52 2005
+++ b/tools/python/xen/lowlevel/xs/xs.c Wed Oct 12 12:00:55 2005
@@ -513,6 +513,7 @@
goto exit;
if (!PyArg_ParseTupleAndKeywords(args, kwds, arg_spec, kwd_spec))
goto exit;
+again:
Py_BEGIN_ALLOW_THREADS
xsval = xs_read_watch(xh, &num);
Py_END_ALLOW_THREADS
@@ -529,8 +530,13 @@
break;
}
if (i == PyList_Size(xsh->watches)) {
- PyErr_SetString(PyExc_RuntimeError, "invalid token");
- goto exit;
+ /* We do not have a registered watch for the one that has just fired.
+ Ignore this -- a watch that has been recently deregistered can still
+ have watches in transit. This is a blocking method, so go back to
+ read again.
+ */
+ free(xsval);
+ goto again;
}
/* Create tuple (path, token). */
val = Py_BuildValue("(sO)", xsval[XS_WATCH_PATH], token);
diff -r 09447f91ab49 -r 00a324b3a2db tools/python/xen/xend/xenstore/xswatch.py
--- a/tools/python/xen/xend/xenstore/xswatch.py Wed Oct 12 11:56:52 2005
+++ b/tools/python/xen/xend/xenstore/xswatch.py Wed Oct 12 12:00:55 2005
@@ -9,6 +9,9 @@
import threading
from xen.lowlevel import xs
from xen.xend.xenstore.xsutil import xshandle
+
+from xen.xend.XendLogging import log
+

class xswatch:

@@ -41,10 +44,13 @@
while True:
try:
we = cls.xs.read_watch()
- except RuntimeError, ex:
- print ex
- raise
- watch = we[1]
- watch.fn(*watch.args, **watch.kwargs)
+ watch = we[1]
+ watch.fn(*watch.args, **watch.kwargs)
+ except:
+ log.exception("read_watch failed")
+ # Ignore this exception -- there's no point throwing it
+ # further on because that will just kill the watcher thread,
+ # which achieves nothing.
+

watchMain = classmethod(watchMain)

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