title: Does calling a c function via ctypes in python release the GIL during execution of the C code
body: <p>I want to call some c function from python to be able to improve performance of my code. But I cannot find online whether when I call a C function using the ctypes libraries the GIL is released. As a simple example:</p>
  <pre><code>from ctypes import *
  fun = cdll.LoadLibrary(&quot;libc.so.6&quot;)
  fun.sleep.argtypes = [c_uint]
  fun.sleep(c_uint(5))
  </code></pre>
  <p>Is the GIL released during the call to <code>fun.sleep</code>?</p>