# HG changeset patch # User john...@sun.com # 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...@sun.com>

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: