1 files changed, 94 insertions, 0 deletions
diff --git a/src/test/validationinterface_tests.cpp b/src/test/validationinterface_tests.cpp
new file mode 100644
index 0000000000..ceba689e52
--- /dev/null
+++ b/src/test/validationinterface_tests.cpp
@@ -0,0 +1,94 @@
+// Copyright (c) 2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <boost/test/unit_test.hpp>
+#include <consensus/validation.h>
+#include <primitives/block.h>
+#include <scheduler.h>
+#include <test/util/setup_common.h>
+#include <util/check.h>
+#include <validationinterface.h>
+
+BOOST_FIXTURE_TEST_SUITE(validationinterface_tests, TestingSetup)
+
+struct TestSubscriberNoop final : public CValidationInterface {
+    void BlockChecked(const CBlock&, const BlockValidationState&) override {}
+};
+
+BOOST_AUTO_TEST_CASE(unregister_validation_interface_race)
+{
+    std::atomic<bool> generate{true};
+
+    // Start thread to generate notifications
+    std::thread gen{[&] {
+        const CBlock block_dummy;
+        BlockValidationState state_dummy;
+        while (generate) {
+            GetMainSignals().BlockChecked(block_dummy, state_dummy);
+        }
+    }};
+
+    // Start thread to consume notifications
+    std::thread sub{[&] {
+        // keep going for about 1 sec, which is 250k iterations
+        for (int i = 0; i < 250000; i++) {
+            auto sub = std::make_shared<TestSubscriberNoop>();
+            RegisterSharedValidationInterface(sub);
+            UnregisterSharedValidationInterface(sub);
+        }
+        // tell the other thread we are done
+        generate = false;
+    }};
+
+    gen.join();
+    sub.join();
+    BOOST_CHECK(!generate);
+}
+
+class TestInterface : public CValidationInterface
+{
+public:
+    TestInterface(std::function<void()> on_call = nullptr, std::function<void()> on_destroy = nullptr)
+        : m_on_call(std::move(on_call)), m_on_destroy(std::move(on_destroy))
+    {
+    }
+    virtual ~TestInterface()
+    {
+        if (m_on_destroy) m_on_destroy();
+    }
+    void BlockChecked(const CBlock& block, const BlockValidationState& state) override
+    {
+        if (m_on_call) m_on_call();
+    }
+    static void Call()
+    {
+        CBlock block;
+        BlockValidationState state;
+        GetMainSignals().BlockChecked(block, state);
+    }
+    std::function<void()> m_on_call;
+    std::function<void()> m_on_destroy;
+};
+
+// Regression test to ensure UnregisterAllValidationInterfaces calls don't
+// destroy a validation interface while it is being called. Bug:
+// https://github.com/bitcoin/bitcoin/pull/18551
+BOOST_AUTO_TEST_CASE(unregister_all_during_call)
+{
+    bool destroyed = false;
+    RegisterSharedValidationInterface(std::make_shared<TestInterface>(
+        [&] {
+            // First call should decrements reference count 2 -> 1
+            UnregisterAllValidationInterfaces();
+            BOOST_CHECK(!destroyed);
+            // Second call should not decrement reference count 1 -> 0
+            UnregisterAllValidationInterfaces();
+            BOOST_CHECK(!destroyed);
+        },
+        [&] { destroyed = true; }));
+    TestInterface::Call();
+    BOOST_CHECK(destroyed);
+}
+
+BOOST_AUTO_TEST_SUITE_END()