Elaborate about the GIL.
diff --git a/Doc/glossary.rst b/Doc/glossary.rst
index 32ad8e3..9ec61de 100644
--- a/Doc/glossary.rst
+++ b/Doc/glossary.rst
@@ -102,9 +102,10 @@
See :pep:`343`.
CPython
- The canonical implementation of the Python programming language. The
- term "CPython" is used in contexts when necessary to distinguish this
- implementation from others such as Jython or IronPython.
+ The canonical implementation of the Python programming language, as
+ distributed on `python.org <http://python.org>`_. The term "CPython"
+ is used when necessary to distinguish this implementation from others
+ such as Jython or IronPython.
decorator
A function returning another function, usually applied as a function
@@ -263,16 +264,25 @@
See :term:`global interpreter lock`.
global interpreter lock
- The lock used by Python threads to assure that only one thread
- executes in the :term:`CPython` :term:`virtual machine` at a time.
- This simplifies the CPython implementation by assuring that no two
- processes can access the same memory at the same time. Locking the
- entire interpreter makes it easier for the interpreter to be
- multi-threaded, at the expense of much of the parallelism afforded by
- multi-processor machines. Efforts have been made in the past to
- create a "free-threaded" interpreter (one which locks shared data at a
- much finer granularity), but so far none have been successful because
- performance suffered in the common single-processor case.
+ The mechanism used by the :term:`CPython` interpreter to assure that
+ only one thread executes Python :term:`bytecode` at a time.
+ This simplifies the CPython implementation by making the object model
+ (including critical built-in types such as :class:`dict`) implicitly
+ safe against concurrent access. Locking the entire interpreter
+ makes it easier for the interpreter to be multi-threaded, at the
+ expense of much of the parallelism afforded by multi-processor
+ machines.
+
+ However, some extension modules, either standard or third-party,
+ are designed so as to release the GIL when doing computationally-intensive
+ tasks such as compression or hashing. Also, the GIL is always released
+ when doing I/O.
+
+ Past efforts to create a "free-threaded" interpreter (one which locks
+ shared data at a much finer granularity) have not been successful
+ because performance suffered in the common single-processor case. It
+ is believed that overcoming this performance issue would make the
+ implementation much more complicated and therefore costlier to maintain.
hashable
An object is *hashable* if it has a hash value which never changes during