Merge #19180: refactor: Replace RecursiveMutex with Mutex in Shutdown()

1a9ef1d refactor: Replace RecursiveMutex with Mutex in Shutdown() (Hennadii Stepanov)

Pull request description:

  Step by step, going to replace all of the `RecursiveMutex` instances with the `Mutex` ones throughout the code base :)

  Not sure if it is possible in all cases though...

  This one is a low-hanging fruit.

ACKs for top commit:
  MarcoFalke:
    ACK 1a9ef1d Shutdown is not recursive, so the same thread can never lock twice (UB)
  vasild:
    ACK 1a9ef1d verified manually that `Shutdown()` is not called from places that could be called from inside `Shutdown()`.

Tree-SHA512: 362a507b1a6f97dc351f708224aedbfe4bee03c4398f394d78ee31c24d76a7012ffff0e6766866cd5fd9a8e0d8840f05a2741111fe583aa20d45f0af3df0dcfa

Author: MarcoFalke

src/init.cpp

@@ -18,6 +18,7 @@
 #include <compat/sanity.h>
 #include <consensus/validation.h>
 #include <fs.h>
+#include <hash.h>
 #include <httprpc.h>
 #include <httpserver.h>
 #include <index/blockfilterindex.h>
@@ -42,6 +43,7 @@
 #include <script/sigcache.h>
 #include <script/standard.h>
 #include <shutdown.h>
+#include <sync.h>
 #include <timedata.h>
 #include <torcontrol.h>
 #include <txdb.h>
@@ -53,8 +55,6 @@
 #include <util/threadnames.h>
 #include <util/translation.h>
 #include <validation.h>
-#include <hash.h>
-
 
 #include <validationinterface.h>
 #include <walletinitinterface.h>
@@ -171,11 +171,10 @@ void Interrupt(NodeContext& node)
 
 void Shutdown(NodeContext& node)
 {
+    static Mutex g_shutdown_mutex;
+    TRY_LOCK(g_shutdown_mutex, lock_shutdown);
+    if (!lock_shutdown) return;
     LogPrintf("%s: In progress...\n", __func__);
-    static RecursiveMutex cs_Shutdown;
-    TRY_LOCK(cs_Shutdown, lockShutdown);
-    if (!lockShutdown)
-        return;
 
     /// Note: Shutdown() must be able to handle cases in which initialization failed part of the way,
     /// for example if the data directory was found to be locked.