From 093e4d38d511c7bb8d48fceebbfd8e350b533075 Mon Sep 17 00:00:00 2001 From: Johannes Erdfelt Date: Wed, 1 Feb 2012 17:07:16 +0000 Subject: Make sure multiple calls to _get_session() aren't nested 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 --- nova/virt/xenapi_conn.py | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'nova') diff --git a/nova/virt/xenapi_conn.py b/nova/virt/xenapi_conn.py index 6b67b8b88..6fda205d0 100644 --- a/nova/virt/xenapi_conn.py +++ b/nova/virt/xenapi_conn.py @@ -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 -- cgit