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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] Have a watch callback return 0 or 1 depending upon whether it would like to
# HG changeset patch
# User emellor@xxxxxxxxxxxxxxxxxxxxxx
# Node ID 210a5b625e30067c8f340452aa1020aa44325124
# Parent 151837f6c26b2cf70d8083915235f4907c9e84a1
Have a watch callback return 0 or 1 depending upon whether it would like to
continue to receive watches. This means that it is not necessary to probe
around in the xswatch internals to unregister a watch.
Tidy up the hotplug watch handling, moving the nested function out to a
separate place (I don't think that this was a problem in the end, but it was
making me nervous as I was debugging the recent race condition, and I find it
clearer out of the class in any case. Pass an integer code representing
hotplug status, once it has been parsed from the store, as there are now a few
different places we can detect failure, and it's cleaner to pass a code from
those places.
Small tidy up to XendDomain, removing the unused releaseDomain field.
diff -r 151837f6c26b -r 210a5b625e30 tools/python/xen/xend/XendDomain.py
--- a/tools/python/xen/xend/XendDomain.py Tue Nov 15 17:47:39 2005
+++ b/tools/python/xen/xend/XendDomain.py Tue Nov 15 18:08:11 2005
@@ -36,6 +36,7 @@
from xen.xend.XendError import XendError
from xen.xend.XendLogging import log
from xen.xend.server import relocate
+from xen.xend.xenstore.xswatch import xswatch
xc = xen.lowlevel.xc.new()
@@ -58,9 +59,11 @@
# to import XendDomain from XendDomainInfo causes unbounded recursion.
# So we stuff the XendDomain instance (self) into xroot's components.
xroot.add_component("xen.xend.XendDomain", self)
+
self.domains = {}
self.domains_lock = threading.RLock()
- self.watchReleaseDomain()
+
+ xswatch("@releaseDomain", self.onReleaseDomain)
self.domains_lock.acquire()
try:
@@ -112,11 +115,7 @@
self.refresh()
finally:
self.domains_lock.release()
-
-
- def watchReleaseDomain(self):
- from xen.xend.xenstore.xswatch import xswatch
- self.releaseDomain = xswatch("@releaseDomain", self.onReleaseDomain)
+ return 1
def xen_domains(self):
diff -r 151837f6c26b -r 210a5b625e30
tools/python/xen/xend/server/DevController.py
--- a/tools/python/xen/xend/server/DevController.py Tue Nov 15 17:47:39 2005
+++ b/tools/python/xen/xend/server/DevController.py Tue Nov 15 18:08:11 2005
@@ -29,6 +29,12 @@
HOTPLUG_STATUS_NODE = "hotplug-status"
HOTPLUG_STATUS_ERROR = "error"
+Connected = 1
+Died = 2
+Error = 3
+Missing = 4
+Timeout = 5
+
xenbusState = {
'Unknown' : 0,
'Initialising' : 1,
@@ -87,18 +93,28 @@
def waitForDevice(self, devid):
log.debug("Waiting for %s.", devid)
- status, fn_ret = self.waitForBackend(devid)
- if status:
+ status = self.waitForBackend(devid)
+
+ if status == Timeout:
self.destroyDevice(devid)
- raise VmError( ("Device %s (%s) could not be connected. "
- "Hotplug scripts not working")
- % (devid, self.deviceClass))
-
- elif fn_ret == HOTPLUG_STATUS_ERROR:
+ raise VmError("Device %s (%s) could not be connected. "
+ "Hotplug scripts not working" %
+ (devid, self.deviceClass))
+
+ elif status == Error:
self.destroyDevice(devid)
- raise VmError( ("Device %s (%s) could not be connected. "
- "Backend device not found!")
- % (devid, self.deviceClass))
+ raise VmError("Device %s (%s) could not be connected. "
+ "Backend device not found" %
+ (devid, self.deviceClass))
+
+ elif status == Missing:
+ raise VmError("Device %s (%s) could not be connected. "
+ "Device not found" % (devid, self.deviceClass))
+
+ elif status == Died:
+ self.destroyDevice(devid)
+ raise VmError("Device %s (%s) could not be connected. "
+ "Device has died" % (devid, self.deviceClass))
def reconfigureDevice(self, devid, config):
@@ -302,35 +318,22 @@
raise
- def waitForBackend(self,devid):
- ev = Event()
-
- def hotplugStatus():
- log.debug("hotplugStatus %d", devid)
-
- try:
- status = self.readBackend(devid, HOTPLUG_STATUS_NODE)
- except VmError:
- status = "died"
- if status is not None:
- watch.xs.unwatch(backpath, watch)
- hotplugStatus.value = status
- ev.set()
-
- hotplugStatus.value = None
+ def waitForBackend(self, devid):
+
frontpath = self.frontendPath(devid)
backpath = xstransact.Read(frontpath, "backend")
if backpath:
- watch = xswatch(backpath, hotplugStatus)
+ statusPath = backpath + '/' + HOTPLUG_STATUS_NODE
+ ev = Event()
+ result = { 'status': Timeout }
+
+ xswatch(statusPath, hotplugStatusCallback, statusPath, ev, result)
ev.wait(DEVICE_CREATE_TIMEOUT)
- if ev.isSet():
- return (0, hotplugStatus.value)
- else:
- return (-1, hotplugStatus.value)
- else:
- return (-1, "missing")
+ return result['status']
+ else:
+ return Missing
def backendPath(self, backdom, devid):
@@ -352,3 +355,25 @@
def frontendMiscPath(self):
return "%s/device-misc/%s" % (self.vm.getDomainPath(),
self.deviceClass)
+
+
+def hotplugStatusCallback(statusPath, ev, result):
+ log.debug("hotplugStatusCallback %s.", statusPath)
+
+ try:
+ status = xstransact.Read(statusPath)
+
+ if status is not None:
+ if status == HOTPLUG_STATUS_ERROR:
+ result['status'] = Error
+ else:
+ result['status'] = Connected
+ else:
+ return 1
+ except VmError:
+ result['status'] = Died
+
+ log.debug("hotplugStatusCallback %d.", result['status'])
+
+ ev.set()
+ return 0
diff -r 151837f6c26b -r 210a5b625e30 tools/python/xen/xend/xenstore/xswatch.py
--- a/tools/python/xen/xend/xenstore/xswatch.py Tue Nov 15 17:47:39 2005
+++ b/tools/python/xen/xend/xenstore/xswatch.py Tue Nov 15 18:08:11 2005
@@ -5,9 +5,7 @@
# Public License. See the file "COPYING" in the main directory of
# this archive for more details.
-import select
import threading
-from xen.lowlevel import xs
from xen.xend.xenstore.xsutil import xshandle
from xen.xend.XendLogging import log
@@ -20,37 +18,42 @@
xslock = threading.Lock()
def __init__(self, path, fn, *args, **kwargs):
+ self.path = path
self.fn = fn
self.args = args
self.kwargs = kwargs
xswatch.watchStart()
xswatch.xs.watch(path, self)
+
def watchStart(cls):
cls.xslock.acquire()
- if cls.watchThread:
+ try:
+ if cls.watchThread:
+ return
+ cls.xs = xshandle()
+ cls.watchThread = threading.Thread(name="Watcher",
+ target=cls.watchMain)
+ cls.watchThread.setDaemon(True)
+ cls.watchThread.start()
+ finally:
cls.xslock.release()
- return
- cls.xs = xshandle()
- cls.watchThread = threading.Thread(name="Watcher",
- target=cls.watchMain)
- cls.watchThread.setDaemon(True)
- cls.watchThread.start()
- cls.xslock.release()
watchStart = classmethod(watchStart)
+
def watchMain(cls):
while True:
try:
we = cls.xs.read_watch()
watch = we[1]
- watch.fn(*watch.args, **watch.kwargs)
+ res = watch.fn(*watch.args, **watch.kwargs)
+ if not res:
+ cls.xs.unwatch(watch.path, watch)
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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