From 48924d585a981113e5ddaef3dfdf92fd7c1e1744 Mon Sep 17 00:00:00 2001
From: Thomas Brain <tbrain@metecs.com>
Date: Wed, 27 Mar 2024 14:20:58 -0500
Subject: [PATCH] python3 GIL locking solution (#1675)

* Implemented use of the python GIL API to replace the less portable mutex solution.

* Replaced nullptr with NULL

---------

Co-authored-by: Thomas Brain <thomas.a.brain@nasa.gov>
---
 include/trick/IPPython.hh                     |  4 ---
 .../sim_services/InputProcessor/IPPython.cpp  | 31 ++++++++++++-------
 2 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/include/trick/IPPython.hh b/include/trick/IPPython.hh
index 6174049a..5e9a8467 100644
--- a/include/trick/IPPython.hh
+++ b/include/trick/IPPython.hh
@@ -17,7 +17,6 @@
 #define IPPYTHON_HH
 
 #include <string>
-#include <pthread.h>
 #include "trick/InputProcessor.hh"
 
 namespace Trick {
@@ -36,9 +35,6 @@ namespace Trick {
             /** Returned value from event condition evaluation.\n */
             int return_val ;                              /**< trick_io(**) trick_units(--) */
 
-            /** Input processor mutex for protection for var server and event processing.\n */
-            pthread_mutex_t ip_mutex;                     /**< trick_io(**) trick_units(--) */
-
             /**
              @brief Constructor.
             */
diff --git a/trick_source/sim_services/InputProcessor/IPPython.cpp b/trick_source/sim_services/InputProcessor/IPPython.cpp
index ce0b1c28..0ecafeea 100644
--- a/trick_source/sim_services/InputProcessor/IPPython.cpp
+++ b/trick_source/sim_services/InputProcessor/IPPython.cpp
@@ -12,10 +12,10 @@
 #include <sstream>
 #include <vector>
 #include <string>
-#include <pthread.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <string.h>
+#include <stdio.h>
 
 #include "trick/IPPython.hh"
 #include "trick/MemoryManager.hh"
@@ -31,6 +31,10 @@ Trick::IPPython::IPPython() : Trick::InputProcessor::InputProcessor() , units_co
     return ;
 }
 
+
+// Need to save the state of the main thread to allow child threads to run PyRun variants.
+static PyThreadState *_save = NULL;
+
 /**
 @details
 -# Loops through all of the memorymanager allocations testing if a name handle was given.
@@ -62,7 +66,9 @@ void Trick::IPPython::get_TMM_named_variables() {
             ss << "trick.castAs" << user_type_name << "(int(" << alloc_info->start << "))" << std::endl ;
             ss << "except AttributeError:" << std::endl ;
             ss << "    pass" << std::endl ;
+            PyGILState_STATE gstate = PyGILState_Ensure();
             PyRun_SimpleString(ss.str().c_str()) ;
+            PyGILState_Release(gstate);
         }
     }
 }
@@ -84,12 +90,6 @@ int Trick::IPPython::init() {
     FILE *input_fp ;
     int ret ;
     std::string error_message ;
-    pthread_mutexattr_t m_attr ;
-
-    /* Initialize a mutex to protect python processing for var server and events. */
-    pthread_mutexattr_init(&m_attr) ;
-    pthread_mutexattr_settype(&m_attr, PTHREAD_MUTEX_RECURSIVE) ;
-    pthread_mutex_init(&ip_mutex , &m_attr) ;
 
     // Run Py_Initialze first for python 2.x
 #if PY_VERSION_HEX < 0x03000000
@@ -104,6 +104,7 @@ int Trick::IPPython::init() {
     Py_Initialize();
 #endif
 
+    // The following PyRun_ calls do not require the PyGILState guards because no threads are launched 
     /* Import simulation specific routines into interpreter. */
     PyRun_SimpleString(
      "import sys\n"
@@ -149,18 +150,21 @@ int Trick::IPPython::init() {
     }
 
     fclose(input_fp) ;
-    return(0) ;
 
+    // Release the GIL from the main thread.
+    Py_UNBLOCK_THREADS
+
+    return(0) ;
 }
 
 //Command to parse the given string.
 int Trick::IPPython::parse(std::string in_string) {
 
     int ret ;
-    pthread_mutex_lock(&ip_mutex);
     in_string += "\n" ;
+    PyGILState_STATE gstate = PyGILState_Ensure();
     ret = PyRun_SimpleString(in_string.c_str()) ;
-    pthread_mutex_unlock(&ip_mutex);
+    PyGILState_Release(gstate);
 
     return ret ;
 
@@ -181,12 +185,12 @@ int Trick::IPPython::parse(std::string in_string) {
 */
 int Trick::IPPython::parse_condition(std::string in_string, int & cond_return_val ) {
 
-    pthread_mutex_lock(&ip_mutex);
     in_string =  std::string("trick_ip.ip.return_val = ") + in_string + "\n" ;
     // Running the simple string will set return_val.
+    PyGILState_STATE gstate = PyGILState_Ensure();
     int py_ret = PyRun_SimpleString(in_string.c_str()) ;
+    PyGILState_Release(gstate);
     cond_return_val = return_val ;
-    pthread_mutex_unlock(&ip_mutex);
 
     return py_ret ;
 
@@ -200,7 +204,10 @@ int Trick::IPPython::restart() {
 }
 
 int Trick::IPPython::shutdown() {
+
     if ( Py_IsInitialized() ) {
+        // Obtain the GIL so that we can shut down properly
+        Py_BLOCK_THREADS
         Py_Finalize();
     }
     return(0) ;