Add GIL section to Contributing-code.md document (cztomczak#102).

cztomczak · cztomczak · commit a5d97f03e176 · 2020-01-16T11:56:45.000+01:00
diff --git a/docs/Contributing-code.md b/docs/Contributing-code.md
@@ -12,6 +12,7 @@ Table of contents:
 * [API docs](#api-docs)
 * [Unit tests](#unit-tests)
 * [Platforms](#platforms)
+* [GIL](#gil)
 * [Authors](#authors)
 * [Updating CEF version](#updating-cef-version)
 
@@ -123,6 +124,24 @@ In most cases new code should run fine on all platforms, but in
 some cases it might be required to test on all platforms before
 PR is merged.
 
+## GIL
+
+In the pxd file, functions should be defined as "nogil" to avoid
+deadlocks when calling CEF functions. In the pyx file the call must
+use the "with nogil" statement.
+
+From [Cython's documentation](http://docs.cython.org/src/userguide/external_C_code.html#acquiring-and-releasing-the-gil):
+
+> Note that acquiring the GIL is a blocking thread-synchronising operation,
+> and therefore potentially costly. It might not be worth releasing the GIL
+> for minor calculations. Usually, I/O operations and substantial computations
+> in parallel code will benefit from it.
+
+Revision [ec1ce78](https://github.com/cztomczak/cefpython/commit/ec1ce788373bb9e0fd2cedd71e900c3877e9185a) removes the GIL lock from the
+following calls: Initialize(), Shutdown(), CreateBrowserSync(),
+SetOsModalLoop(), QuitMessageLoop(), CefExecuteProcess(). There still
+might be some more functions from which the GIL lock should be removed.
+
 ## Authors
 
 In your pull request modify also the [Authors](../Authors) file
