From a59b6694ff9b216b5632079522a47df46c464b9b Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Wed, 30 Mar 2022 14:50:30 -0700
Subject: [PATCH] Interrupt handling

---
 Modules/signalmodule.c | 38 ++++++++++++++++++++++++++++++++++++++
 Python/ceval.c         | 28 ++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+)

diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c
index 96881d4a49..1926f650b6 100644
--- a/Modules/signalmodule.c
+++ b/Modules/signalmodule.c
@@ -1768,11 +1768,49 @@ PyErr_CheckSignals(void)
     return _PyErr_CheckSignalsTstate(tstate);
 }
 
+#if defined(__EMSCRIPTEN__)
+
+#include <emscripten.h>
+EM_JS(int, _Py_CheckEmscriptenSignals_Helper, (void), {
+    if (!Module.Py_EmscriptenSignalBuffer) {
+        return 0;
+    }
+    try {
+        let result = Module.Py_EmscriptenSignalBuffer[0];
+        Module.Py_EmscriptenSignalBuffer[0] = 0;
+        return result;
+    } catch(e) {
+#if !defined(NDEBUG)
+        console.warn("Error occurred while trying to read signal buffer:", e);
+#endif
+        return 0;
+    }
+});
+
+EMSCRIPTEN_KEEPALIVE int Py_EMSCRIPTEN_SIGNAL_HANDLING = 0;
+
+void
+_Py_CheckEmscriptenSignals(void)
+{
+    if (!Py_EMSCRIPTEN_SIGNAL_HANDLING) {
+        return;
+    }
+    int signal = _Py_CheckEmscriptenSignals_Helper();
+    if (signal) {
+        PyErr_SetInterruptEx(signal);
+    }
+}
+
+#endif
 
 /* Declared in cpython/pyerrors.h */
 int
 _PyErr_CheckSignalsTstate(PyThreadState *tstate)
 {
+    #if defined(__EMSCRIPTEN__)
+    _Py_CheckEmscriptenSignals();
+    #endif
+
     if (!_Py_atomic_load(&is_tripped)) {
         return 0;
     }
diff --git a/Python/ceval.c b/Python/ceval.c
index ab10b4166d..5ed67ee398 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -1152,6 +1152,30 @@ PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
     return _PyEval_EvalFrame(tstate, f, throwflag);
 }
 
+#if defined(__EMSCRIPTEN__)
+
+extern int Py_EMSCRIPTEN_SIGNAL_HANDLING;
+void _Py_CheckEmscriptenSignals(void);
+
+#define PY_EMSCRIPTEN_SIGNAL_INTERVAL 50
+
+static int
+emscripten_signal_clock = PY_EMSCRIPTEN_SIGNAL_INTERVAL;
+
+static void
+_Py_CheckEmscriptenSignalsPeriodically()
+{
+    if (!Py_EMSCRIPTEN_SIGNAL_HANDLING) {
+        return;
+    }
+    emscripten_signal_clock--;
+    if (emscripten_signal_clock == 0) {
+        emscripten_signal_clock = PY_EMSCRIPTEN_SIGNAL_INTERVAL;
+        _Py_CheckEmscriptenSignals();
+    }
+}
+
+#endif
 
 /* Handle signals, pending calls, GIL drop request
    and asynchronous exception */
@@ -1742,6 +1766,10 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, PyFrameObject *f, int throwflag)
         assert(STACK_LEVEL() <= co->co_stacksize);  /* else overflow */
         assert(!_PyErr_Occurred(tstate));
 
+        #if defined(__EMSCRIPTEN__)
+        _Py_CheckEmscriptenSignalsPeriodically();
+        #endif
+
         /* Do periodic things.  Doing this every time through
            the loop would add too much overhead, so we do it
            only every Nth instruction.  We also do it if
-- 
2.25.1