Examples of widely-used software applications using user-level threads?

Can somebody give me an开发者_运维技巧 example of widely-used software applications that use user-level threads. Here by 'user-level' threads I mean threads that are implemented entirely in user-space and are unknown to the kernel.

I would say most web browsers IE, Firefox, Chromium/Chrome do so. For Chromium, a new user thread is created whenever you create a new tab.