Do not arbitrarily release Python GIL in HLTControlFlowMgr

!3340 (merged) introduced an unconditional release of Python GIL while the problem should have been handled in Gaudi as done in gaudi/Gaudi!1369 (merged) and gaudi/Gaudi!1387 (merged). Moreover the unconditional release of the GIL prevent running the HLTControlFlowMgr from Gaudi.exe (for example in test workflows like gaudirun.py -n -o myopts.opts some_complicated_options.py && Gaudi.exe myopts.opts).

Hlt/HLTScheduler/src/HLTControlFlowMgr.cpp

@@ -38,7 +38,6 @@
 #include "ThreadPool.h"
 #include "tbb/task_arena.h"
 #include "tbb/task_scheduler_observer.h"
-#include <Python.h>
 #include <algorithm>
 #include <chrono>
 #include <condition_variable>
@@ -322,13 +321,6 @@ namespace {
     void             on_scheduler_entry( bool ) override { m_thread_count++; }
     void             on_scheduler_exit( bool ) override { m_thread_count--; }
   };
-
-  /// Helper class to temporarily release the GIL to allow other threads to take it.
-  struct PyGILReleaseGuard {
-    PyGILReleaseGuard() : state( PyEval_SaveThread() ) {}
-    ~PyGILReleaseGuard() { PyEval_RestoreThread( state ); }
-    PyThreadState* state;
-  };
 } // namespace
 
 StatusCode HLTControlFlowMgr::initialize() {
@@ -841,50 +833,44 @@ StatusCode HLTControlFlowMgr::nextEvent( int maxevt ) {
                             []( uint64_t total, auto const& counter ) { return total + counter.sum().count(); } );
   };
 
-  {
-    // Release the GIL so that XMLSummarySvc can acquire it from within the event execution thread.
-    // Probably XMLSummarySvc fails with multiple threads but it should be redone anyway.
-    PyGILReleaseGuard gilRelease;
-
-    while ( maxevt < 0 || m_nextevt < maxevt ) {
-      if ( m_shutdown_now ) {
-        shutdown_threadpool();
-        while ( not empty() ) pop();
-        return StatusCode::FAILURE;
-      }
-      if ( m_startTimeAtEvt == m_nextevt ) {
-        auto currtime = std::time( nullptr );
-        info() << "Timing started at: " << std::put_time( std::localtime( &currtime ), "%T" ) << endmsg;
-        m_alloc_tracker->beginTracking();
-        startTimeAndTicks.emplace( Clock::now(), getTotalWorkerTicks() );
-      }
-      if ( m_stopTimeAtEvt == m_nextevt ) {
-        endTimeAndTicks.emplace( Clock::now(), getTotalWorkerTicks() );
-        m_alloc_tracker->endTracking();
-        auto currtime = std::time( nullptr );
-        info() << "Timing stopped at: " << std::put_time( std::localtime( &currtime ), "%T" ) << endmsg;
-      }
-      auto evtContext = createEventContext();
-      if ( !evtContext.valid() ) {
-        if ( m_nextevt == -1 ) break; // finished
-        shutdown_threadpool();
-        return StatusCode::FAILURE; // else we have an success --> exit loop
-      }
-      push( std::move( evtContext ) );
-      pop();
-    } // end main loop on finished events
-
-    if ( !endTimeAndTicks ) {
+  while ( maxevt < 0 || m_nextevt < maxevt ) {
+    if ( m_shutdown_now ) {
+      shutdown_threadpool();
+      while ( not empty() ) pop();
+      return StatusCode::FAILURE;
+    }
+    if ( m_startTimeAtEvt == m_nextevt ) {
+      auto currtime = std::time( nullptr );
+      info() << "Timing started at: " << std::put_time( std::localtime( &currtime ), "%T" ) << endmsg;
+      m_alloc_tracker->beginTracking();
+      startTimeAndTicks.emplace( Clock::now(), getTotalWorkerTicks() );
+    }
+    if ( m_stopTimeAtEvt == m_nextevt ) {
       endTimeAndTicks.emplace( Clock::now(), getTotalWorkerTicks() );
-      m_stopTimeAtEvt = m_finishedEvt;
       m_alloc_tracker->endTracking();
+      auto currtime = std::time( nullptr );
+      info() << "Timing stopped at: " << std::put_time( std::localtime( &currtime ), "%T" ) << endmsg;
+    }
+    auto evtContext = createEventContext();
+    if ( !evtContext.valid() ) {
+      if ( m_nextevt == -1 ) break; // finished
+      shutdown_threadpool();
+      return StatusCode::FAILURE; // else we have an success --> exit loop
     }
+    push( std::move( evtContext ) );
+    pop();
+  } // end main loop on finished events
+
+  if ( !endTimeAndTicks ) {
+    endTimeAndTicks.emplace( Clock::now(), getTotalWorkerTicks() );
+    m_stopTimeAtEvt = m_finishedEvt;
+    m_alloc_tracker->endTracking();
+  }
 
-    shutdown_threadpool();
-    while ( not empty() ) pop();
+  shutdown_threadpool();
+  while ( not empty() ) pop();
 
-    releaseEvtSelContext().ignore();
-  }
+  releaseEvtSelContext().ignore();
 
   if ( !startTimeAndTicks ) {
     info() << "---> Loop over " << m_finishedEvt << " Events Finished - "