# HG changeset patch
# User john.levon@xxxxxxx
# Date 1198248324 28800
# Node ID b29e155a85ef663170b0651798c84db79bafcdd8
# Parent d7974e8d8f5131356e7c8fc87f880d737044e91b
Fix xend xenstore handling.
xend can get into a situation where two processes are attempting to
interact with the xenstore socket, with disastrous results. Fix the two
bad users of xstransact, add a big warning, and fix the destructor so
future mistakes will be detected earlier.
Signed-off-by: John Levon <john.levon@xxxxxxx>
diff --git a/tools/python/xen/xend/XendDomainInfo.py
b/tools/python/xen/xend/XendDomainInfo.py
--- a/tools/python/xen/xend/XendDomainInfo.py
+++ b/tools/python/xen/xend/XendDomainInfo.py
@@ -1533,10 +1533,9 @@ class XendDomainInfo:
except:
# Log and swallow any exceptions in removal --
# there's nothing more we can do.
- log.exception("Device release failed: %s; %s; %s",
- self.info['name_label'], devclass, dev)
-
-
+ log.exception("Device release failed: %s; %s; %s",
+ self.info['name_label'], devclass, dev)
+ t.abort()
def getDeviceController(self, name):
"""Get the device controller for this domain, and if it
@@ -1848,7 +1847,6 @@ class XendDomainInfo:
# build list of phantom devices to be removed after normal devices
plist = []
if self.domid is not None:
- from xen.xend.xenstore.xstransact import xstransact
t = xstransact("%s/device/vbd" % GetDomainPath(self.domid))
for dev in t.list():
backend_phantom_vbd =
xstransact.Read("%s/device/vbd/%s/phantom_vbd" \
@@ -1858,6 +1856,7 @@ class XendDomainInfo:
% backend_phantom_vbd)
plist.append(backend_phantom_vbd)
plist.append(frontend_phantom_vbd)
+ t.abort()
return plist
def _cleanup_phantom_devs(self, plist):
diff --git a/tools/python/xen/xend/server/pciif.py
b/tools/python/xen/xend/server/pciif.py
--- a/tools/python/xen/xend/server/pciif.py
+++ b/tools/python/xen/xend/server/pciif.py
@@ -22,8 +22,6 @@ from xen.xend import sxp
from xen.xend import sxp
from xen.xend.XendError import VmError
from xen.xend.XendLogging import log
-
-from xen.xend.xenstore.xstransact import xstransact
from xen.xend.server.DevController import DevController
diff --git a/tools/python/xen/xend/xenstore/xstransact.py
b/tools/python/xen/xend/xenstore/xstransact.py
--- a/tools/python/xen/xend/xenstore/xstransact.py
+++ b/tools/python/xen/xend/xenstore/xstransact.py
@@ -7,8 +7,16 @@
from xen.xend.xenstore.xsutil import xshandle
+class xstransact:
+ """WARNING: Be very careful if you're instantiating an xstransact object
+ yourself (i.e. not using the capitalized static helpers like .Read().
+ It is essential that you clean up the object in place via
+ t.commit/abort(): GC can happen at any time, including contexts where
+ it's not safe to to use the shared xenstore socket fd. In particular,
+ if xend forks, and GC occurs, we can have two processes trying to
+ use the same xenstore fd, and all hell breaks loose.
+ """
-class xstransact:
def __init__(self, path = ""):
@@ -22,8 +30,9 @@ class xstransact:
self.in_transaction = True
def __del__(self):
+ # see above.
if self.in_transaction:
- xshandle().transaction_end(self.transaction, True)
+ raise RuntimeError("ERROR: GC of live transaction")
def commit(self):
if not self.in_transaction:
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