init: Signal m_tip_block_cv on Ctrl-C

Signal m_tip_block_cv when Ctrl-C is pressed or SIGTERM is received, the same
way it is currently signalled when the `stop` RPC is called. This lets RPC
calls like `waitforblockheight` and IPC calls like `waitTipChanged` be
interrupted, instead of waiting for their original timeouts and delaying
shutdown.

Historical notes:

- The behavior where `stop` RPC signals `m_tip_block_cv`, but CTRL-C does not,
  has been around since the condition variable was introduced in #30409
  (7eccdaf160).
- The signaling was later moved without changing behavior in #30967
  (5ca28ef28b). This commit moves it again to
  the Interrupt() function, which is probably the place it should have been
  added initially, so it works for Ctrl-C shutdowns as well as `stop`
  shutdowns.
- A Qt shutdown bug calling wait methods was fixed previously in #18452
  (da73f1513a), and this change updates that
  fix to avoid the hang happening again in Qt.

src/init.cpp

@@ -215,8 +215,6 @@ void InitContext(NodeContext& node)
     node.shutdown_request = [&node] {
         assert(node.shutdown_signal);
         if (!(*node.shutdown_signal)()) return false;
-        // Wake any threads that may be waiting for the tip to change.
-        if (node.notifications) WITH_LOCK(node.notifications->m_tip_block_mutex, node.notifications->m_tip_block_cv.notify_all());
         return true;
     };
 }
@@ -267,6 +265,8 @@ void Interrupt(NodeContext& node)
 #if HAVE_SYSTEM
     ShutdownNotify(*node.args);
 #endif
+    // Wake any threads that may be waiting for the tip to change.
+    if (node.notifications) WITH_LOCK(node.notifications->m_tip_block_mutex, node.notifications->m_tip_block_cv.notify_all());
     InterruptHTTPServer();
     InterruptHTTPRPC();
     InterruptRPC();

src/node/interfaces.cpp

@@ -132,7 +132,6 @@ public:
     }
     void appShutdown() override
     {
-        Interrupt(*m_context);
         Shutdown(*m_context);
     }
     void startShutdown() override
@@ -141,12 +140,7 @@ public:
         if (!(Assert(ctx.shutdown_request))()) {
             LogError("Failed to send shutdown signal\n");
         }
-
-        // Stop RPC for clean shutdown if any of waitfor* commands is executed.
-        if (args().GetBoolArg("-server", false)) {
-            InterruptRPC();
-            StopRPC();
-        }
+        Interrupt(*m_context);
     }
     bool shutdownRequested() override { return ShutdownRequested(*Assert(m_context)); };
     bool isSettingIgnored(const std::string& name) override

test/functional/feature_init.py

@@ -12,7 +12,6 @@ import signal
 import subprocess
 import time
 
-from test_framework.authproxy import JSONRPCException
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.test_node import (
     BITCOIN_PID_FILENAME_DEFAULT,
@@ -251,9 +250,8 @@ class InitTest(BitcoinTestFramework):
         terminal. (This can be different than the node shutdown sequence that
         happens when the stop RPC is sent.)
 
-        Currently when the break signal is sent, it does not interrupt the
-        waitforblockheight RPC call, and the node does not exit until it times
-        out."""
+        The waitforblockheight call should be interrupted and return right away,
+        and not time out."""
 
         self.log.info("Testing waitforblockheight RPC call followed by break signal")
         node = self.nodes[0]
@@ -287,12 +285,9 @@ class InitTest(BitcoinTestFramework):
                 node.process.send_signal(signal.SIGTERM)
             node.process.wait()
 
-            try:
             result = fut.result()
-                raise Exception(f"waitforblockheight returned {result!r}")
-            except JSONRPCException as e:
-                self.log.debug(f"waitforblockheight raised {e!r}")
-                assert_equal(e.error['code'], -344) # -344 is RPC timeout
+            self.log.debug(f"waitforblockheight returned {result!r}")
+            assert_equal(result["height"], current_height)
             node.wait_until_stopped()
 
     def run_test(self):