On Thu, Dec 20, 2012 at 05:47:40PM -0800, Gregory P. Smith wrote:
> On Thu, Dec 20, 2012 at 10:43 AM, Trent Nelson <tr...@snakebite.org>
> wrote:
>
> This seems odd to me so I wanted to see what others think. The unit
> test Lib/unittest/test/test_runner.py:Test_TextRunner.test_warnings
> will eventually hit subprocess.Popen._communicate.
>
> The `mswindows` implementation of this method relies on threads to
> buffer stdin/stdout. That'll eventually result in
> PyOs_StdioReadline
> being called without the GIL being held. PyOs_StdioReadline calls
> PyMem_MALLOC, PyMem_FREE and possibly PyMem_REALLOC.
>
> Those threads are implemented in Python so how would the GIL ever not be
> held?
> -gps
PyOS_Readline drops the GIL prior to calling PyOS_StdioReadline:
Py_BEGIN_ALLOW_THREADS
--------^^^^^^^^^^^^^^^^^^^^^^
#ifdef WITH_THREAD
PyThread_acquire_lock(_PyOS_ReadlineLock, 1);
#endif
/* This is needed to handle the unlikely case that the
* interpreter is in interactive mode *and* stdin/out are not
* a tty. This can happen, for example if python is run like
* this: python -i < test1.py
*/
if (!isatty (fileno (sys_stdin)) || !isatty (fileno (sys_stdout)))
rv = PyOS_StdioReadline (sys_stdin, sys_stdout, prompt);
-----------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
else
rv = (*PyOS_ReadlineFunctionPointer)(sys_stdin, sys_stdout,
prompt);
Py_END_ALLOW_THREADS
Trent.
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