Merge #17737: Add ChainstateManager, remove BlockManager global

c9017ce3bc27665594c9d80f395780d40755bb22 protect g_chainman with cs_main (James O'Beirne)
2b081c4568e8019886fdb0f2a57babc73d7487f7 test: add basic tests for ChainstateManager (James O'Beirne)
4ae29f5f0c5117032debb722d7049664fdceeae8 use ChainstateManager to initialize chainstate (James O'Beirne)
5b690f0aae21e7d46cbefe3f5be645842ac4ae3b refactor: move RewindBlockIndex to CChainState (James O'Beirne)
89cdf4d5692d396b8c7177b3918aa9dab07f9624 validation: introduce unused ChainstateManager (James O'Beirne)
8e2ecfe2496d8a015f3ee8723025a438feffbd28 validation: add CChainState.m_from_snapshot_blockhash (James O'Beirne)

Pull request description:

  This is part of the [assumeutxo project](https://github.com/bitcoin/bitcoin/projects/11):

  Parent PR: #15606
  Issue: #15605
  Specification: https://github.com/jamesob/assumeutxo-docs/tree/master/proposal

  ---

  This changeset introduces `ChainstateManager`, which is responsible for creating and managing access to multiple chainstates. Until we allow chainstate creation from UTXO snapshots (next assumeutxo PR?) it's basically unnecessary, but it is a prerequisite for background IBD support.

  Changes are also made to the initialization process to make use of `g_chainman` and thus clear the way for multiple chainstates being loaded on startup.

  One immediate benefit of this change is that we no longer have the `g_blockman` global, but instead have the ChainstateManager inject a reference of its shared BlockManager into any chainstate it creates.

  Another immediate benefit is that uses of `ChainActive()` and `ChainstateActive()` are now covered by lock annotations. Because use of `g_chainman` is annotated to require cs_main, these two functions subsequently follow.

  Because of whitespace changes, this diff looks bigger than it is. E.g., 4813167d98 is most easily reviewed with
  ```sh
  git show --color-moved=dimmed_zebra -w 4813167d98
  ```

ACKs for top commit:
  MarcoFalke:
    re-ACK c9017ce3bc27665594c9d80f395780d40755bb22 📙
  fjahr:
    Code Review Re-ACK c9017ce3bc27665594c9d80f395780d40755bb22
  ariard:
    Code Review ACK c9017ce
  ryanofsky:
    Code review ACK c9017ce3bc27665594c9d80f395780d40755bb22. No changes since last review other than a straight rebase

Tree-SHA512: 3f250d0dc95d4bfd70852ef1e39e081a4a9b71a4453f276e6d474c2ae06ad6ae6a32b4173084fe499e1e9af72dd9007f4a8a375c63ce9ac472ffeaada41ab508

2 files changed, 107 insertions, 2 deletions

diff --git a/src/test/util/setup_common.cpp b/src/test/util/setup_common.cpp
index 29ec144c49..32d50e49b9 100644
--- a/src/test/util/setup_common.cpp
+++ b/src/test/util/setup_common.cpp
@@ -114,7 +114,8 @@ TestingSetup::TestingSetup(const std::string& chainName) : BasicTestingSetup(cha
     GetMainSignals().RegisterBackgroundSignalScheduler(*g_rpc_node->scheduler);
 
     pblocktree.reset(new CBlockTreeDB(1 << 20, true));
-    g_chainstate = MakeUnique<CChainState>();
+
+    g_chainman.InitializeChainstate();
     ::ChainstateActive().InitCoinsDB(
         /* cache_size_bytes */ 1 << 23, /* in_memory */ true, /* should_wipe */ false);
     assert(!::ChainstateActive().CanFlushToDisk());
@@ -161,7 +162,7 @@ TestingSetup::~TestingSetup()
     m_node.mempool = nullptr;
     m_node.scheduler.reset();
     UnloadBlockIndex();
-    g_chainstate.reset();
+    g_chainman.Reset();
     pblocktree.reset();
 }
 
diff --git a/src/test/validation_chainstatemanager_tests.cpp b/src/test/validation_chainstatemanager_tests.cpp
new file mode 100644
index 0000000000..6e7186db22
--- /dev/null
+++ b/src/test/validation_chainstatemanager_tests.cpp
@@ -0,0 +1,104 @@
+// Copyright (c) 2019 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+//
+#include <chainparams.h>
+#include <random.h>
+#include <uint256.h>
+#include <consensus/validation.h>
+#include <sync.h>
+#include <test/util/setup_common.h>
+#include <validation.h>
+
+#include <vector>
+
+#include <boost/test/unit_test.hpp>
+
+BOOST_FIXTURE_TEST_SUITE(validation_chainstatemanager_tests, TestingSetup)
+
+//! Basic tests for ChainstateManager.
+//!
+//! First create a legacy (IBD) chainstate, then create a snapshot chainstate.
+BOOST_AUTO_TEST_CASE(chainstatemanager)
+{
+    ChainstateManager manager;
+    std::vector<CChainState*> chainstates;
+    const CChainParams& chainparams = Params();
+
+    // Create a legacy (IBD) chainstate.
+    //
+    ENTER_CRITICAL_SECTION(cs_main);
+    CChainState& c1 = manager.InitializeChainstate();
+    LEAVE_CRITICAL_SECTION(cs_main);
+    chainstates.push_back(&c1);
+    c1.InitCoinsDB(
+        /* cache_size_bytes */ 1 << 23, /* in_memory */ true, /* should_wipe */ false);
+    WITH_LOCK(::cs_main, c1.InitCoinsCache());
+
+    BOOST_CHECK(!manager.IsSnapshotActive());
+    BOOST_CHECK(!manager.IsSnapshotValidated());
+    BOOST_CHECK(!manager.IsBackgroundIBD(&c1));
+    auto all = manager.GetAll();
+    BOOST_CHECK_EQUAL_COLLECTIONS(all.begin(), all.end(), chainstates.begin(), chainstates.end());
+
+    auto& active_chain = manager.ActiveChain();
+    BOOST_CHECK_EQUAL(&active_chain, &c1.m_chain);
+
+    BOOST_CHECK_EQUAL(manager.ActiveHeight(), -1);
+
+    auto active_tip = manager.ActiveTip();
+    auto exp_tip = c1.m_chain.Tip();
+    BOOST_CHECK_EQUAL(active_tip, exp_tip);
+
+    auto& validated_cs = manager.ValidatedChainstate();
+    BOOST_CHECK_EQUAL(&validated_cs, &c1);
+
+    // Create a snapshot-based chainstate.
+    //
+    ENTER_CRITICAL_SECTION(cs_main);
+    CChainState& c2 = manager.InitializeChainstate(GetRandHash());
+    LEAVE_CRITICAL_SECTION(cs_main);
+    chainstates.push_back(&c2);
+    c2.InitCoinsDB(
+        /* cache_size_bytes */ 1 << 23, /* in_memory */ true, /* should_wipe */ false);
+    WITH_LOCK(::cs_main, c2.InitCoinsCache());
+    // Unlike c1, which doesn't have any blocks. Gets us different tip, height.
+    c2.LoadGenesisBlock(chainparams);
+    BlockValidationState _;
+    BOOST_CHECK(c2.ActivateBestChain(_, chainparams, nullptr));
+
+    BOOST_CHECK(manager.IsSnapshotActive());
+    BOOST_CHECK(!manager.IsSnapshotValidated());
+    BOOST_CHECK(manager.IsBackgroundIBD(&c1));
+    BOOST_CHECK(!manager.IsBackgroundIBD(&c2));
+    auto all2 = manager.GetAll();
+    BOOST_CHECK_EQUAL_COLLECTIONS(all2.begin(), all2.end(), chainstates.begin(), chainstates.end());
+
+    auto& active_chain2 = manager.ActiveChain();
+    BOOST_CHECK_EQUAL(&active_chain2, &c2.m_chain);
+
+    BOOST_CHECK_EQUAL(manager.ActiveHeight(), 0);
+
+    auto active_tip2 = manager.ActiveTip();
+    auto exp_tip2 = c2.m_chain.Tip();
+    BOOST_CHECK_EQUAL(active_tip2, exp_tip2);
+
+    // Ensure that these pointers actually correspond to different
+    // CCoinsViewCache instances.
+    BOOST_CHECK(exp_tip != exp_tip2);
+
+    auto& validated_cs2 = manager.ValidatedChainstate();
+    BOOST_CHECK_EQUAL(&validated_cs2, &c1);
+
+    auto& validated_chain = manager.ValidatedChain();
+    BOOST_CHECK_EQUAL(&validated_chain, &c1.m_chain);
+
+    auto validated_tip = manager.ValidatedTip();
+    exp_tip = c1.m_chain.Tip();
+    BOOST_CHECK_EQUAL(validated_tip, exp_tip);
+
+    // Avoid triggering the address sanitizer.
+    WITH_LOCK(::cs_main, manager.Unload());
+}
+
+BOOST_AUTO_TEST_SUITE_END()