When an I/O error occurs on a non-container thread only dispatch to a container thread to handle the error if using Servlet 3+ asynchronous processing. This avoids potential deadlocks if an application is performing I/O on a non-container thread without using the Servlet 3+ asynchronous API.

https://bz.apache.org/bugzilla/show_bug.cgi?id=57779
http://svn.apache.org/viewvc?view=revision&revision=1670632