Fix interrupt handling issues in csp: ensure first node is stopped and reset signaled flag across runs (#206)

* Fix various interrupt handling issues in csp

Signed-off-by: Adam Glustein <[email protected]>

* Add comment explaining signal handling in multiple engine threads

Signed-off-by: Adam Glustein <[email protected]>

---------

Signed-off-by: Adam Glustein <[email protected]>

Author: AdamGlustein

cpp/csp/engine/RootEngine.cpp

@@ -11,12 +11,24 @@
 namespace csp
 {
 
-static volatile bool    g_SIGNALED = false;
+static volatile int     g_SIGNAL_COUNT = 0;
+/*
+The signal count variable is maintained to ensure that multiple engine threads shutdown properly.
+
+An interrupt should cause all running engines to stop, but should not affect future runs in the same process.
+Thus, each root engine keeps track of the signal count when its created. When an interrupt occurs, one engine thread
+handles the interrupt by incrementing the count. Then, all other root engines detect the signal by comparing their
+initial count to the current count. 
+
+Future runs after the interrupt remain unaffected since they are initialized with the updated signal count, and will
+only consider themselves "interupted" if another signal is received during their execution.
+*/
+
 static struct sigaction g_prevSIGTERMaction;
 
 static void handle_SIGTERM( int signum )
 {
-    g_SIGNALED = true;
+    g_SIGNAL_COUNT++;
     if( g_prevSIGTERMaction.sa_handler )
         (*g_prevSIGTERMaction.sa_handler)( signum );
 }
@@ -58,6 +70,7 @@ RootEngine::RootEngine( const Dictionary & settings ) : Engine( m_cycleStepTable
                                                         m_cycleCount( 0 ),
                                                         m_settings( settings ),
                                                         m_inRealtime( false ),
+                                                        m_initSignalCount( g_SIGNAL_COUNT ),
                                                         m_pushEventQueue( m_settings.queueWaitTime > TimeDelta::ZERO() )
 {
     if( settings.get<bool>( "profile",  false ) )
@@ -78,7 +91,7 @@ RootEngine::~RootEngine()
 
 bool RootEngine::interrupted() const
 {
-    return g_SIGNALED;
+    return g_SIGNAL_COUNT != m_initSignalCount;
 }
 
 void RootEngine::preRun( DateTime start, DateTime end )
@@ -131,7 +144,7 @@ void RootEngine::processEndCycle()
 void RootEngine::runSim( DateTime end )
 {
     m_inRealtime = false;
-    while( m_scheduler.hasEvents() && m_state == State::RUNNING && !g_SIGNALED )
+    while( m_scheduler.hasEvents() && m_state == State::RUNNING && !interrupted() )
     {
         m_now = m_scheduler.nextTime();
         if( m_now > end )
@@ -161,7 +174,7 @@ void RootEngine::runRealtime( DateTime end )
 
     m_inRealtime = true;
     bool haveEvents = false;
-    while( m_state == State::RUNNING && !g_SIGNALED )
+    while( m_state == State::RUNNING && !interrupted() )
     {
         TimeDelta waitTime;
         if( !m_pendingPushEvents.hasEvents() )

cpp/csp/engine/RootEngine.h

@@ -127,6 +127,7 @@ class RootEngine : public Engine
     PendingPushEvents m_pendingPushEvents;
     Settings          m_settings;
     bool              m_inRealtime;
+    int               m_initSignalCount;
 
     PushEventQueue    m_pushEventQueue;
 

cpp/csp/python/PyNode.cpp

@@ -212,18 +212,17 @@ void PyNode::start()
 
 void PyNode::stop()
 {
-    PyObjectPtr rv = PyObjectPtr::own( PyObject_CallMethod( m_gen.ptr(), "close", nullptr ) );
-    if( !rv.ptr() )
+    if( this -> rootEngine() -> interrupted() && PyErr_CheckSignals() == -1 )
     {
-        if( PyErr_Occurred() == PyExc_KeyboardInterrupt )
-        {
-            PyErr_Clear();
-            rv = PyObjectPtr::own( PyObject_CallMethod( m_gen.ptr(), "close", nullptr ) );
-        }
-
-        if( !rv.ptr() )
-            CSP_THROW( PythonPassthrough, "" );
+        // When an interrupt occurs a KeyboardInterrupt exception is raised in Python, which we need to clear
+        // before calling "close" on the generator. Else, the close method will fail due to the unhandled 
+        // exception, and we lose the state of the generator before the "finally" block that calls stop() is executed.
+        PyErr_Clear();
     }
+
+    PyObjectPtr rv = PyObjectPtr::own( PyObject_CallMethod( m_gen.ptr(), "close", nullptr ) );
+    if( !rv.ptr() )
+        CSP_THROW( PythonPassthrough, "" );
 }
 
 PyNode * PyNode::create( PyEngine * pyengine, PyObject * inputs, PyObject * outputs, PyObject * gen )

cpp/csp/python/csptestlibimpl.cpp

@@ -66,13 +66,45 @@ EXPORT_CPPNODE( start_n2_throw );
 
 }
 
+namespace interrupt_stop_test
+{
+
+using namespace csp::python;
+
+void setStatus( const DialectGenericType & obj_, int64_t idx )
+{
+    PyObjectPtr obj = PyObjectPtr::own( toPython( obj_ ) );
+    PyObjectPtr list = PyObjectPtr::own( PyObject_GetAttrString( obj.get(), "stopped" ) );
+    PyList_SET_ITEM( list.get(), idx, Py_True );
+}
+
+DECLARE_CPPNODE( set_stop_index )
+{
+    INIT_CPPNODE( set_stop_index ) {}
+
+    SCALAR_INPUT( DialectGenericType, obj_ );
+    SCALAR_INPUT( int64_t, idx );
+
+    START() {}
+    INVOKE() {}
+
+    STOP()
+    {
+       setStatus( obj_, idx );
+    }
+};
+EXPORT_CPPNODE( set_stop_index );
+
+}
+
 }
 
 }
 
 // Test nodes
 REGISTER_CPPNODE( csp::cppnodes::testing::stop_start_test, start_n1_set_value );
 REGISTER_CPPNODE( csp::cppnodes::testing::stop_start_test, start_n2_throw );
+REGISTER_CPPNODE( csp::cppnodes::testing::interrupt_stop_test, set_stop_index );
 
 static PyModuleDef _csptestlibimpl_module = {
     PyModuleDef_HEAD_INIT,

csp/tests/test_engine.py

@@ -2064,6 +2064,60 @@ def g() -> ts[int]:
         csp.run(g, starttime=datetime(2020, 1, 1), endtime=timedelta())
         self.assertTrue(status["started"] and status["stopped"])
 
+    def test_interrupt_stops_all_nodes(self):
+        @csp.node
+        def n(l: list, idx: int):
+            with csp.stop():
+                l[idx] = True
+
+        @csp.node
+        def raise_interrupt():
+            with csp.alarms():
+                a = csp.alarm(bool)
+            with csp.start():
+                csp.schedule_alarm(a, timedelta(seconds=1), True)
+            if csp.ticked(a):
+                import signal
+                os.kill(os.getpid(), signal.SIGINT)
+            
+        # Python nodes
+        @csp.graph
+        def g(l: list):
+            n(l, 0)
+            n(l, 1)
+            n(l, 2)
+            raise_interrupt()
+
+        stopped = [False, False, False]
+        with self.assertRaises(KeyboardInterrupt):
+            csp.run(g, stopped, starttime=datetime.utcnow(), endtime=timedelta(seconds=60), realtime=True)
+
+        for element in stopped:
+            self.assertTrue(element)
+        
+        # C++ nodes
+        class RTI:
+            def __init__(self):
+                self.stopped = [False, False, False]
+        
+        @csp.node(cppimpl=_csptestlibimpl.set_stop_index)
+        def n2(obj_: object, idx: int):
+            return
+
+        @csp.graph
+        def g2(rti: RTI):
+            n2(rti, 0)
+            n2(rti, 1)
+            n2(rti, 2)
+            raise_interrupt()
+
+        rti = RTI()
+        with self.assertRaises(KeyboardInterrupt):
+            csp.run(g2, rti, starttime=datetime.utcnow(), endtime=timedelta(seconds=60), realtime=True)
+        
+        for element in rti.stopped:
+            self.assertTrue(element)
+
 
 if __name__ == "__main__":
     unittest.main()