openstack/nova
Code Issues Proposed changes

Make sure multiple calls to _get_session() aren't nested

Browse Source 
Fixes bug 924918

async_call_plugin() acquires a xenapi session as does the nested call to
get_xenapi_host(). This can cause a deadlock if multiple greenthreads
all block waiting for the outer sessions to be freed to allocate the
inner session. This change moves the call to get_xenapi_host() to outside
the with statement to ensure calls to _get_session() aren't nested.

Change-Id: I8f5490f40a9ccaf74a276187f66519a5d5f52b2e
This commit is contained in:
Johannes Erdfelt
2012-02-01 17:07:16 +00:00
parent 8908d8ba49
commit 093e4d38d5
1 changed files with 5 additions and 1 deletions
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6
nova/virt/xenapi_conn.py
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@@ -544,10 +544,14 @@ class XenAPISession(object):
def async_call_plugin(self, plugin, fn, args):
"""Call Async.host.call_plugin on a background thread."""
# NOTE(johannes): Fetch host before we acquire a session. Since
# _get_session() acquires a session too, it can result in a deadlock
# if multiple greenthreads race with each other. See bug 924918
host = self.get_xenapi_host()
with self._get_session() as session:
return tpool.execute(self._unwrap_plugin_exceptions,
session.xenapi.Async.host.call_plugin,
self.get_xenapi_host(), plugin, fn, args)
host, plugin, fn, args)
def wait_for_task(self, task, uuid=None):
"""Return the result of the given task. The task is polled