Incorrect Lock Ordering on SessionVar When Called from CometActor Constructor

[djspiewak]

When accessing a session variable from the constructor of a CometActor, deadlock will sometimes occur (usually with another comet thread already running against the session). The issue is comet actors are created from within LiftSession#findComet, which locks the session. If you access a SessionVar during this construction process, you will then lock the corresponding variable. However, most often it is the variable which locks first, and then the session (e.g. when accessing a session var during the normal course of execution). This of course can lead to deadlock when one thread is attempting to access a session var while another thread is creating a comet actor.

[dpp]

More granular sync'ing session vars closed by 4986cefb055810ca08c1595aacfaf206d22e99b6

[github-importer]

Imported from GitHub: http://github.com/dpp/liftweb/issues/42/find

[github-importer]

Imported from Assembla: http://www.assembla.com/spaces/liftweb/tickets/42