diff --git a/src/validationinterface.h b/src/validationinterface.h
--- a/src/validationinterface.h
+++ b/src/validationinterface.h
@@ -8,6 +8,7 @@
 
 #include "primitives/transaction.h" // CTransaction(Ref)
 
+#include <functional>
 #include <memory>
 
 class CBlock;
@@ -31,6 +32,16 @@
 void UnregisterValidationInterface(CValidationInterface *pwalletIn);
 /** Unregister all wallets from core */
 void UnregisterAllValidationInterfaces();
+/**
+ * Pushes a function to callback onto the notification queue, guaranteeing any
+ * callbacks generated prior to now are finished when the function is called.
+ *
+ * Be very careful blocking on func to be called if any locks are held -
+ * validation interface clients may not be able to make progress as they often
+ * wait for things like cs_main, so blocking until func is called with cs_main
+ * will result in a deadlock (that DEBUG_LOCKORDER will miss).
+ */
+void CallFunctionInValidationInterfaceQueue(std::function<void()> func);
 
 class CValidationInterface {
 protected:
@@ -110,6 +121,8 @@
     friend void ::RegisterValidationInterface(CValidationInterface *);
     friend void ::UnregisterValidationInterface(CValidationInterface *);
     friend void ::UnregisterAllValidationInterfaces();
+    friend void ::CallFunctionInValidationInterfaceQueue(
+        std::function<void()> func);
 
     void MempoolEntryRemoved(CTransactionRef tx, MemPoolRemovalReason reason);
 
diff --git a/src/validationinterface.cpp b/src/validationinterface.cpp
--- a/src/validationinterface.cpp
+++ b/src/validationinterface.cpp
@@ -136,6 +136,10 @@
     g_signals.m_internals->NewPoWValidBlock.disconnect_all_slots();
 }
 
+void CallFunctionInValidationInterfaceQueue(std::function<void()> func) {
+    g_signals.m_internals->m_schedulerClient.AddToProcessQueue(std::move(func));
+}
+
 void CMainSignals::MempoolEntryRemoved(CTransactionRef ptx,
                                        MemPoolRemovalReason reason) {
     if (reason != MemPoolRemovalReason::BLOCK &&