Give CMainSignals a reference to the global scheduler

...so that it can run some signals in the background later

src/init.cpp

@@ -251,6 +251,7 @@ void Shutdown()
     }
 #endif
     UnregisterAllValidationInterfaces();
+    GetMainSignals().UnregisterBackgroundSignalScheduler();
 #ifdef ENABLE_WALLET
     for (CWalletRef pwallet : vpwallets) {
         delete pwallet;
@@ -1203,6 +1204,8 @@ bool AppInitMain(boost::thread_group& threadGroup, CScheduler& scheduler)
     CScheduler::Function serviceLoop = boost::bind(&CScheduler::serviceQueue, &scheduler);
     threadGroup.create_thread(boost::bind(&TraceThread<CScheduler::Function>, "scheduler", serviceLoop));
 
+    GetMainSignals().RegisterBackgroundSignalScheduler(scheduler);
+
     /* Start the RPC server already.  It will be started in "warmup" mode
      * and not really process calls already (but it will signify connections
      * that the server is there and will be ready later).  Warmup mode will

src/test/test_bitcoin.cpp

@@ -62,6 +62,12 @@ TestingSetup::TestingSetup(const std::string& chainName) : BasicTestingSetup(cha
         pathTemp = GetTempPath() / strprintf("test_bitcoin_%lu_%i", (unsigned long)GetTime(), (int)(InsecureRandRange(100000)));
         fs::create_directories(pathTemp);
         ForceSetArg("-datadir", pathTemp.string());
+
+        // Note that because we don't bother running a scheduler thread here,
+        // callbacks via CValidationInterface are unreliable, but that's OK,
+        // our unit tests aren't testing multiple parts of the code at once.
+        GetMainSignals().RegisterBackgroundSignalScheduler(scheduler);
+
         mempool.setSanityCheck(1.0);
         pblocktree = new CBlockTreeDB(1 << 20, true);
         pcoinsdbview = new CCoinsViewDB(1 << 23, true);
@@ -88,6 +94,7 @@ TestingSetup::~TestingSetup()
         UnregisterNodeSignals(GetNodeSignals());
         threadGroup.interrupt_all();
         threadGroup.join_all();
+        GetMainSignals().UnregisterBackgroundSignalScheduler();
         UnloadBlockIndex();
         delete pcoinsTip;
         delete pcoinsdbview;

src/test/test_bitcoin.h

@@ -10,6 +10,7 @@
 #include "key.h"
 #include "pubkey.h"
 #include "random.h"
+#include "scheduler.h"
 #include "txdb.h"
 #include "txmempool.h"
 
@@ -53,6 +54,7 @@ struct TestingSetup: public BasicTestingSetup {
     fs::path pathTemp;
     boost::thread_group threadGroup;
     CConnman* connman;
+    CScheduler scheduler;
 
     TestingSetup(const std::string& chainName = CBaseChainParams::MAIN);
     ~TestingSetup();

src/validationinterface.cpp

@@ -4,6 +4,8 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include "validationinterface.h"
+#include "init.h"
+#include "scheduler.h"
 
 #include <boost/signals2/signal.hpp>
 
@@ -17,6 +19,8 @@ struct MainSignalsInstance {
     boost::signals2::signal<void (int64_t nBestBlockTime, CConnman* connman)> Broadcast;
     boost::signals2::signal<void (const CBlock&, const CValidationState&)> BlockChecked;
     boost::signals2::signal<void (const CBlockIndex *, const std::shared_ptr<const CBlock>&)> NewPoWValidBlock;
+
+    CScheduler *m_scheduler = NULL;
 };
 
 static CMainSignals g_signals;
@@ -25,6 +29,15 @@ CMainSignals::CMainSignals() {
     m_internals.reset(new MainSignalsInstance());
 }
 
+void CMainSignals::RegisterBackgroundSignalScheduler(CScheduler& scheduler) {
+    assert(!m_internals->m_scheduler);
+    m_internals->m_scheduler = &scheduler;
+}
+
+void CMainSignals::UnregisterBackgroundSignalScheduler() {
+    m_internals->m_scheduler = NULL;
+}
+
 CMainSignals& GetMainSignals()
 {
     return g_signals;

src/validationinterface.h

@@ -19,6 +19,7 @@ class CReserveScript;
 class CValidationInterface;
 class CValidationState;
 class uint256;
+class CScheduler;
 
 // These functions dispatch to one or all registered wallets
 
@@ -72,9 +73,15 @@ class CMainSignals {
     friend void ::RegisterValidationInterface(CValidationInterface*);
     friend void ::UnregisterValidationInterface(CValidationInterface*);
     friend void ::UnregisterAllValidationInterfaces();
+
 public:
     CMainSignals();
 
+    /** Register a CScheduler to give callbacks which should run in the background (may only be called once) */
+    void RegisterBackgroundSignalScheduler(CScheduler& scheduler);
+    /** Unregister a CScheduler to give callbacks which should run in the background - these callbacks will now be dropped! */
+    void UnregisterBackgroundSignalScheduler();
+
     void UpdatedBlockTip(const CBlockIndex *, const CBlockIndex *, bool fInitialDownload);
     void TransactionAddedToMempool(const CTransactionRef &);
     void BlockConnected(const std::shared_ptr<const CBlock> &, const CBlockIndex *pindex, const std::vector<CTransactionRef> &);