Merge bitcoin#30967: refactor: Replace g_genesis_wait_cv with m_tip_b…

…lock_cv

fa22e5c refactor: Remove dead code that assumed tip == nullptr (MarcoFalke)
fa2e443 refactor: Replace g_genesis_wait_cv with m_tip_block_cv (MarcoFalke)
fa7f52a refactor: Use wait_for predicate to check for interrupt (MarcoFalke)
5ca28ef refactor: Split up NodeContext shutdown_signal and shutdown_request (Ryan Ofsky)
fad8e7f bugfix: Mark m_tip_block_cv as guarded by m_tip_block_mutex (MarcoFalke)
fa18586 refactor: Add missing GUARDED_BY(m_tip_block_mutex) (MarcoFalke)
fa4c075 doc: Clarify waitTipChanged docs (MarcoFalke)

Pull request description:

  `g_genesis_wait_cv` is similar to `m_tip_block_cv` but shuffling everything through a redundant `boost::signals2`.

  So remove it, along with some other dead code, as well as minor fixups.

ACKs for top commit:
  ryanofsky:
    Code review ACK fa22e5c (just rebased since last review)
  Sjors:
    ACK fa22e5c
  TheCharlatan:
    ACK fa22e5c

Tree-SHA512: a2cb59b651aaf85a3574723adfe403487566788ad945933b0458816ccc841fce08ca77b31afbd2d6adb5bf1deed7229c028bee74fb4bbaf6576e9edcfa0ad817

src/bitcoind.cpp

@@ -274,7 +274,7 @@ MAIN_FUNCTION
     if (ProcessInitCommands(args)) return EXIT_SUCCESS;
 
     // Start application
-    if (!AppInit(node) || !Assert(node.shutdown)->wait()) {
+    if (!AppInit(node) || !Assert(node.shutdown_signal)->wait()) {
         node.exit_status = EXIT_FAILURE;
     }
     Interrupt(node);

src/index/base.cpp

@@ -31,7 +31,7 @@ template <typename... Args>
 void BaseIndex::FatalErrorf(util::ConstevalFormatString<sizeof...(Args)> fmt, const Args&... args)
 {
     auto message = tfm::format(fmt, args...);
-    node::AbortNode(m_chain->context()->shutdown, m_chain->context()->exit_status, Untranslated(message), m_chain->context()->warnings.get());
+    node::AbortNode(m_chain->context()->shutdown_request, m_chain->context()->exit_status, Untranslated(message), m_chain->context()->warnings.get());
 }
 
 CBlockLocator GetLocator(interfaces::Chain& chain, const uint256& block_hash)

src/init.cpp

@@ -207,7 +207,14 @@ void InitContext(NodeContext& node)
     g_shutdown.emplace();
 
     node.args = &gArgs;
-    node.shutdown = &*g_shutdown;
+    node.shutdown_signal = &*g_shutdown;
+    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;
+    };
 }
 
 //////////////////////////////////////////////////////////////////////////////
@@ -235,7 +242,7 @@ void InitContext(NodeContext& node)
 
 bool ShutdownRequested(node::NodeContext& node)
 {
-    return bool{*Assert(node.shutdown)};
+    return bool{*Assert(node.shutdown_signal)};
 }
 
 #if HAVE_SYSTEM
@@ -286,7 +293,7 @@ void Shutdown(NodeContext& node)
 
     StopHTTPRPC();
     StopREST();
-    StopRPC(&node);
+    StopRPC();
     StopHTTPServer();
     for (const auto& client : node.chain_clients) {
         client->flush();
@@ -678,21 +685,6 @@ void SetupServerArgs(ArgsManager& argsman, bool can_listen_ipc)
     argsman.AddHiddenArgs(hidden_args);
 }
 
-static bool fHaveGenesis = false;
-static GlobalMutex g_genesis_wait_mutex;
-static std::condition_variable g_genesis_wait_cv;
-
-static void BlockNotifyGenesisWait(const CBlockIndex* pBlockIndex)
-{
-    if (pBlockIndex != nullptr) {
-        {
-            LOCK(g_genesis_wait_mutex);
-            fHaveGenesis = true;
-        }
-        g_genesis_wait_cv.notify_all();
-    }
-}
-
 #if HAVE_SYSTEM
 static void StartupNotify(const ArgsManager& args)
 {
@@ -707,7 +699,7 @@ static void StartupNotify(const ArgsManager& args)
 static bool AppInitServers(NodeContext& node)
 {
     const ArgsManager& args = *Assert(node.args);
-    if (!InitHTTPServer(*Assert(node.shutdown))) {
+    if (!InitHTTPServer(*Assert(node.shutdown_signal))) {
         return false;
     }
     StartRPC();
@@ -1216,7 +1208,7 @@ static ChainstateLoadResult InitAndLoadChainstate(
     };
     Assert(ApplyArgsManOptions(args, blockman_opts)); // no error can happen, already checked in AppInitParameterInteraction
     try {
-        node.chainman = std::make_unique<ChainstateManager>(*Assert(node.shutdown), chainman_opts, blockman_opts);
+        node.chainman = std::make_unique<ChainstateManager>(*Assert(node.shutdown_signal), chainman_opts, blockman_opts);
     } catch (std::exception& e) {
         return {ChainstateLoadStatus::FAILURE_FATAL, strprintf(Untranslated("Failed to initialize ChainstateManager: %s"), e.what())};
     }
@@ -1327,7 +1319,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
         constexpr uint64_t min_disk_space = 50 << 20; // 50 MB
         if (!CheckDiskSpace(args.GetBlocksDirPath(), min_disk_space)) {
             LogError("Shutting down due to lack of disk space!\n");
-            if (!(*Assert(node.shutdown))()) {
+            if (!(Assert(node.shutdown_request))()) {
                 LogError("Failed to send shutdown signal after disk space check\n");
             }
         }
@@ -1608,8 +1600,9 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
 
     // ********************************************************* Step 7: load block chain
 
-    node.notifications = std::make_unique<KernelNotifications>(*Assert(node.shutdown), node.exit_status, *Assert(node.warnings));
-    ReadNotificationArgs(args, *node.notifications);
+    node.notifications = std::make_unique<KernelNotifications>(Assert(node.shutdown_request), node.exit_status, *Assert(node.warnings));
+    auto& kernel_notifications{*node.notifications};
+    ReadNotificationArgs(args, kernel_notifications);
 
     // cache size calculations
     CacheSizes cache_sizes = CalculateCacheSizes(args, g_enabled_filter_types.size());
@@ -1649,7 +1642,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
             return false;
         }
         do_reindex = true;
-        if (!Assert(node.shutdown)->reset()) {
+        if (!Assert(node.shutdown_signal)->reset()) {
             LogError("Internal error: failed to reset shutdown signal.\n");
         }
         std::tie(status, error) = InitAndLoadChainstate(
@@ -1761,15 +1754,6 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
         }
     }
 
-    // Either install a handler to notify us when genesis activates, or set fHaveGenesis directly.
-    // No locking, as this happens before any background thread is started.
-    boost::signals2::connection block_notify_genesis_wait_connection;
-    if (WITH_LOCK(chainman.GetMutex(), return chainman.ActiveChain().Tip() == nullptr)) {
-        block_notify_genesis_wait_connection = uiInterface.NotifyBlockTip_connect(std::bind(BlockNotifyGenesisWait, std::placeholders::_2));
-    } else {
-        fHaveGenesis = true;
-    }
-
 #if HAVE_SYSTEM
     const std::string block_notify = args.GetArg("-blocknotify", "");
     if (!block_notify.empty()) {
@@ -1794,7 +1778,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
         ImportBlocks(chainman, vImportFiles);
         if (args.GetBoolArg("-stopafterblockimport", DEFAULT_STOPAFTERBLOCKIMPORT)) {
             LogPrintf("Stopping after block import\n");
-            if (!(*Assert(node.shutdown))()) {
+            if (!(Assert(node.shutdown_request))()) {
                 LogError("Failed to send shutdown signal after finishing block import\n");
             }
             return;
@@ -1814,15 +1798,11 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
     });
 
     // Wait for genesis block to be processed
-    {
-        WAIT_LOCK(g_genesis_wait_mutex, lock);
-        // We previously could hang here if shutdown was requested prior to
-        // ImportBlocks getting started, so instead we just wait on a timer to
-        // check ShutdownRequested() regularly.
-        while (!fHaveGenesis && !ShutdownRequested(node)) {
-            g_genesis_wait_cv.wait_for(lock, std::chrono::milliseconds(500));
-        }
-        block_notify_genesis_wait_connection.disconnect();
+    if (WITH_LOCK(chainman.GetMutex(), return chainman.ActiveTip() == nullptr)) {
+        WAIT_LOCK(kernel_notifications.m_tip_block_mutex, lock);
+        kernel_notifications.m_tip_block_cv.wait(lock, [&]() EXCLUSIVE_LOCKS_REQUIRED(kernel_notifications.m_tip_block_mutex) {
+            return !kernel_notifications.m_tip_block.IsNull() || ShutdownRequested(node);
+        });
     }
 
     if (ShutdownRequested(node)) {
@@ -1831,17 +1811,17 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
 
     // ********************************************************* Step 12: start node
 
-    //// debug print
     int64_t best_block_time{};
     {
-        LOCK(cs_main);
+        LOCK(chainman.GetMutex());
+        const auto& tip{*Assert(chainman.ActiveTip())};
         LogPrintf("block tree size = %u\n", chainman.BlockIndex().size());
-        chain_active_height = chainman.ActiveChain().Height();
-        best_block_time = chainman.ActiveChain().Tip() ? chainman.ActiveChain().Tip()->GetBlockTime() : chainman.GetParams().GenesisBlock().GetBlockTime();
+        chain_active_height = tip.nHeight;
+        best_block_time = tip.GetBlockTime();
         if (tip_info) {
             tip_info->block_height = chain_active_height;
             tip_info->block_time = best_block_time;
-            tip_info->verification_progress = GuessVerificationProgress(chainman.GetParams().TxData(), chainman.ActiveChain().Tip());
+            tip_info->verification_progress = GuessVerificationProgress(chainman.GetParams().TxData(), &tip);
         }
         if (tip_info && chainman.m_best_header) {
             tip_info->header_height = chainman.m_best_header->nHeight;

src/interfaces/mining.h

@@ -61,11 +61,11 @@ class Mining
     virtual std::optional<BlockRef> getTip() = 0;
 
     /**
-     * Waits for the tip to change
+     * Waits for the connected tip to change. If the tip was not connected on
+     * startup, this will wait.
      *
      * @param[in] current_tip block hash of the current chain tip. Function waits
-     *                        for the chain tip to change if this matches, otherwise
-     *                        it returns right away.
+     *                        for the chain tip to differ from this.
      * @param[in] timeout     how long to wait for a new tip
      * @returns               Hash and height of the current chain tip after this call.
      */

src/node/abort.cpp

@@ -15,12 +15,12 @@
 
 namespace node {
 
-void AbortNode(util::SignalInterrupt* shutdown, std::atomic<int>& exit_status, const bilingual_str& message, node::Warnings* warnings)
+void AbortNode(const std::function<bool()>& shutdown_request, std::atomic<int>& exit_status, const bilingual_str& message, node::Warnings* warnings)
 {
     if (warnings) warnings->Set(Warning::FATAL_INTERNAL_ERROR, message);
     InitError(_("A fatal internal error occurred, see debug.log for details: ") + message);
     exit_status.store(EXIT_FAILURE);
-    if (shutdown && !(*shutdown)()) {
+    if (shutdown_request && !shutdown_request()) {
         LogError("Failed to send shutdown signal\n");
     };
 }

src/node/abort.h

@@ -6,16 +6,13 @@
 #define BITCOIN_NODE_ABORT_H
 
 #include <atomic>
+#include <functional>
 
 struct bilingual_str;
 
-namespace util {
-class SignalInterrupt;
-} // namespace util
-
 namespace node {
 class Warnings;
-void AbortNode(util::SignalInterrupt* shutdown, std::atomic<int>& exit_status, const bilingual_str& message, node::Warnings* warnings);
+void AbortNode(const std::function<bool()>& shutdown_request, std::atomic<int>& exit_status, const bilingual_str& message, node::Warnings* warnings);
 } // namespace node
 
 #endif // BITCOIN_NODE_ABORT_H

src/node/context.h

@@ -59,8 +59,10 @@ struct NodeContext {
     std::unique_ptr<ECC_Context> ecc_context;
     //! Init interface for initializing current process and connecting to other processes.
     interfaces::Init* init{nullptr};
+    //! Function to request a shutdown.
+    std::function<bool()> shutdown_request;
     //! Interrupt object used to track whether node shutdown was requested.
-    util::SignalInterrupt* shutdown{nullptr};
+    util::SignalInterrupt* shutdown_signal{nullptr};
     std::unique_ptr<AddrMan> addrman;
     std::unique_ptr<CConnman> connman;
     std::unique_ptr<CTxMemPool> mempool;

src/node/interfaces.cpp

@@ -134,13 +134,15 @@ class NodeImpl : public Node
     }
     void startShutdown() override
     {
-        if (!(*Assert(Assert(m_context)->shutdown))()) {
+        NodeContext& ctx{*Assert(m_context)};
+        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(m_context);
+            StopRPC();
         }
     }
     bool shutdownRequested() override { return ShutdownRequested(*Assert(m_context)); };
@@ -938,19 +940,12 @@ class MinerImpl : public Mining
 
     BlockRef waitTipChanged(uint256 current_tip, MillisecondsDouble timeout) override
     {
-        // Interrupt check interval
-        const MillisecondsDouble tick{1000};
-        auto now{std::chrono::steady_clock::now()};
-        auto deadline = now + timeout;
-        // std::chrono does not check against overflow
-        if (deadline < now) deadline = std::chrono::steady_clock::time_point::max();
+        if (timeout > std::chrono::years{100}) timeout = std::chrono::years{100}; // Upper bound to avoid UB in std::chrono
         {
             WAIT_LOCK(notifications().m_tip_block_mutex, lock);
-            while ((notifications().m_tip_block == uint256() || notifications().m_tip_block == current_tip) && !chainman().m_interrupt) {
-                now = std::chrono::steady_clock::now();
-                if (now >= deadline) break;
-                notifications().m_tip_block_cv.wait_until(lock, std::min(deadline, now + tick));
-            }
+            notifications().m_tip_block_cv.wait_for(lock, timeout, [&]() EXCLUSIVE_LOCKS_REQUIRED(notifications().m_tip_block_mutex) {
+                return (notifications().m_tip_block != current_tip && notifications().m_tip_block != uint256::ZERO) || chainman().m_interrupt;
+            });
         }
         // Must release m_tip_block_mutex before locking cs_main, to avoid deadlocks.
         LOCK(::cs_main);

src/node/kernel_notifications.cpp

@@ -58,7 +58,7 @@ kernel::InterruptResult KernelNotifications::blockTip(SynchronizationState state
 
     uiInterface.NotifyBlockTip(state, &index);
     if (m_stop_at_height && index.nHeight >= m_stop_at_height) {
-        if (!m_shutdown()) {
+        if (!m_shutdown_request()) {
             LogError("Failed to send shutdown signal after reaching stop height\n");
         }
         return kernel::Interrupted{};
@@ -90,12 +90,12 @@ void KernelNotifications::warningUnset(kernel::Warning id)
 
 void KernelNotifications::flushError(const bilingual_str& message)
 {
-    AbortNode(&m_shutdown, m_exit_status, message, &m_warnings);
+    AbortNode(m_shutdown_request, m_exit_status, message, &m_warnings);
 }
 
 void KernelNotifications::fatalError(const bilingual_str& message)
 {
-    node::AbortNode(m_shutdown_on_fatal_error ? &m_shutdown : nullptr,
+    node::AbortNode(m_shutdown_on_fatal_error ? m_shutdown_request : nullptr,
                     m_exit_status, message, &m_warnings);
 }
 

src/node/kernel_notifications.h

@@ -13,6 +13,7 @@
 
 #include <atomic>
 #include <cstdint>
+#include <functional>
 
 class ArgsManager;
 class CBlockIndex;
@@ -23,10 +24,6 @@ namespace kernel {
 enum class Warning;
 } // namespace kernel
 
-namespace util {
-class SignalInterrupt;
-} // namespace util
-
 namespace node {
 
 class Warnings;
@@ -35,8 +32,8 @@ static constexpr int DEFAULT_STOPATHEIGHT{0};
 class KernelNotifications : public kernel::Notifications
 {
 public:
-    KernelNotifications(util::SignalInterrupt& shutdown, std::atomic<int>& exit_status, node::Warnings& warnings)
-        : m_shutdown(shutdown), m_exit_status{exit_status}, m_warnings{warnings} {}
+    KernelNotifications(const std::function<bool()>& shutdown_request, std::atomic<int>& exit_status, node::Warnings& warnings)
+        : m_shutdown_request(shutdown_request), m_exit_status{exit_status}, m_warnings{warnings} {}
 
     [[nodiscard]] kernel::InterruptResult blockTip(SynchronizationState state, CBlockIndex& index) override EXCLUSIVE_LOCKS_REQUIRED(!m_tip_block_mutex);
 
@@ -58,12 +55,14 @@ class KernelNotifications : public kernel::Notifications
     bool m_shutdown_on_fatal_error{true};
 
     Mutex m_tip_block_mutex;
-    std::condition_variable m_tip_block_cv;
+    std::condition_variable m_tip_block_cv GUARDED_BY(m_tip_block_mutex);
     //! The block for which the last blockTip notification was received for.
-    uint256 m_tip_block;
+    //! The initial ZERO means that no block has been connected yet, which may
+    //! be true even long after startup, until shutdown.
+    uint256 m_tip_block GUARDED_BY(m_tip_block_mutex){uint256::ZERO};
 
 private:
-    util::SignalInterrupt& m_shutdown;
+    const std::function<bool()>& m_shutdown_request;
     std::atomic<int>& m_exit_status;
     node::Warnings& m_warnings;
 };

src/rpc/server.cpp

@@ -169,7 +169,7 @@ static RPCHelpMan stop()
 {
     // Event loop will exit after current HTTP requests have been handled, so
     // this reply will get back to the client.
-    CHECK_NONFATAL((*CHECK_NONFATAL(EnsureAnyNodeContext(jsonRequest.context).shutdown))());
+    CHECK_NONFATAL((CHECK_NONFATAL(EnsureAnyNodeContext(jsonRequest.context).shutdown_request))());
     if (jsonRequest.params[0].isNum()) {
         UninterruptibleSleep(std::chrono::milliseconds{jsonRequest.params[0].getInt<int>()});
     }
@@ -294,7 +294,7 @@ void InterruptRPC()
     });
 }
 
-void StopRPC(const std::any& context)
+void StopRPC()
 {
     static std::once_flag g_rpc_stop_flag;
     // This function could be called twice if the GUI has been started with -server=1.
@@ -303,9 +303,6 @@ void StopRPC(const std::any& context)
         LogDebug(BCLog::RPC, "Stopping RPC\n");
         WITH_LOCK(g_deadline_timers_mutex, deadlineTimers.clear());
         DeleteAuthCookie();
-        node::NodeContext& node = EnsureAnyNodeContext(context);
-        // The notifications interface doesn't exist between initialization step 4a and 7.
-        if (node.notifications) node.notifications->m_tip_block_cv.notify_all();
         LogDebug(BCLog::RPC, "RPC stopped.\n");
     });
 }