From 1a84cc007e207f2dd61f86a7fc3d86632fdce72f Mon Sep 17 00:00:00 2001
From: Kumar Aditya <59607654+kumaraditya303@users.noreply.github.com>
Date: Wed, 8 Mar 2023 13:29:39 +0530
Subject: [PATCH] GH-102397: Fix segfault from race condition in signal
 handling (#102399)

Co-authored-by: Gregory P. Smith <greg@krypto.org>
---
 Lib/test/test_signal.py                           | 15 +++++++++++++++
 ...2023-03-04-06-48-34.gh-issue-102397.ACJaOf.rst |  2 ++
 Modules/signalmodule.c                            |  4 ++++
 3 files changed, 21 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Core and Builtins/2023-03-04-06-48-34.gh-issue-102397.ACJaOf.rst

diff --git a/Lib/test/test_signal.py b/Lib/test/test_signal.py
index 2562a57ea42..25afd6aabe0 100644
--- a/Lib/test/test_signal.py
+++ b/Lib/test/test_signal.py
@@ -1406,6 +1406,21 @@ class RaiseSignalTest(unittest.TestCase):
         signal.raise_signal(signal.SIGINT)
         self.assertTrue(is_ok)
 
+    def test__thread_interrupt_main(self):
+        # See https://github.com/python/cpython/issues/102397
+        code = """if 1:
+        import _thread
+        class Foo():
+            def __del__(self):
+                _thread.interrupt_main()
+
+        x = Foo()
+        """
+
+        rc, out, err = assert_python_ok('-c', code)
+        self.assertIn(b'OSError: Signal 2 ignored due to race condition', err)
+
+
 
 class PidfdSignalTest(unittest.TestCase):
 
diff --git a/Misc/NEWS.d/next/Core and Builtins/2023-03-04-06-48-34.gh-issue-102397.ACJaOf.rst b/Misc/NEWS.d/next/Core and Builtins/2023-03-04-06-48-34.gh-issue-102397.ACJaOf.rst
new file mode 100644
index 00000000000..db0b3f32c2e
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2023-03-04-06-48-34.gh-issue-102397.ACJaOf.rst	
@@ -0,0 +1,2 @@
+Fix segfault from race condition in signal handling during garbage collection.
+Patch by Kumar Aditya.
diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c
index cd26eca351c..0e472e1ee4f 100644
--- a/Modules/signalmodule.c
+++ b/Modules/signalmodule.c
@@ -148,6 +148,10 @@ get_signal_state(PyObject *module)
 static inline int
 compare_handler(PyObject *func, PyObject *dfl_ign_handler)
 {
+    // See https://github.com/python/cpython/pull/102399
+    if (func == NULL || dfl_ign_handler == NULL) {
+        return 0;
+    }
     assert(PyLong_CheckExact(dfl_ign_handler));
     if (!PyLong_CheckExact(func)) {
         return 0;