# What's new in PyPy 2.5.1

Non-blocking file reads sometimes raised EAGAIN even though they had buffered data waiting, fixed in b1c4fcb04a42

Fix a bug in cpyext in multithreaded programs acquiring/releasing the GIL

Avoid tracing all stack roots during repeated minor collections, by ignoring the part of the stack that didn't change

Update stdlib to version 2.7.9

Fix exception being raised by kqueue.control (CPython compatibility)

Refactor rpython.flowspace.framestate.FrameState.

Add an alternative location to save LastError, errno around ctypes, cffi external calls so things like pdb will not overwrite it

Speed up the warmup times of the JIT by removing a quadratic algorithm in the heapcache.

Simplify flow graphs on the fly during annotation phase.