Merge #16127: More thread safety annotation coverage

5478d6c099e76fe070703cc5383cba7b91468b0f logging: thread safety annotations (Anthony Towns)
e685ca19928eec4e687c66f5edfcfff085a42c27 util/system.cpp: add thread safety annotations for dir_locks (Anthony Towns)
a7887899480db72328784009181d93904e6d479d test/checkqueue_tests: thread safety annotations (Anthony Towns)
479c5846f7477625ec275fbb8a076c7ef157172b rpc/blockchain.cpp: thread safety annotations for latestblock (Anthony Towns)
8b5af3d4c1270267ad85e78f661bf8fab06f3aad net: fMsgProcWake use LOCK instead of lock_guard (Anthony Towns)
de7c5f41aba860751ef7824245e6d9d5088a1200 wallet/wallet.h: Remove mutexScanning which was only protecting a single atomic bool (Anthony Towns)
c3cf2f55013c4ea1c1ef4a878fc7ff8e92f2c42d rpc/blockchain.cpp: Remove g_utxosetscan mutex that is only protecting a single atomic variable (Anthony Towns)

Pull request description:

  In a few cases we need to use `std::mutex` rather than the sync.h primitives. But `std::lock_guard<std::mutex>` doesn't include the clang thread safety annotations unless you also use clang's C library, which means you can't indicate when variables should be guarded by `std::mutex` mutexes.

  This adds an annotated version of `std::lock_guard<std::mutex>` to threadsafety.h to fix that, and modifies places where `std::mutex` is used to take advantage of the annotations.

  It's based on top of #16112, and turns the thread safety comments included there into annotations.

  It also changes the RAII classes in wallet/wallet.h and rpc/blockchain.cpp to just use the atomic<bool> flag for synchronisation rather than having a mutex that doesn't actually guard anything as well.

ACKs for top commit:
  MarcoFalke:
    ACK 5478d6c099e76fe070703cc5383cba7b91468b0f 🗾
  hebasto:
    re-ACK 5478d6c099e76fe070703cc5383cba7b91468b0f, only renamed s/`MutexGuard`/`LockGuard`/, and dropped the commit "test/util_threadnames_tests: add thread safety annotations" since the [previous](https://github.com/bitcoin/bitcoin/pull/16127#pullrequestreview-414184113) review.
  ryanofsky:
    Code review ACK 5478d6c099e76fe070703cc5383cba7b91468b0f. Thanks for taking suggestions! Only changes since last review are dropping thread rename test commit d53072ec730d8eec5a5b72f7e65a54b141e62b19 and renaming mutex guard to lock guard

Tree-SHA512: 7b00d31f6f2b5a222ec69431eb810a74abf0542db3a65d1bbad54e354c40df2857ec89c00b4a5e466c81ba223267ca95f3f98d5fbc1a1d052a2c3a7d2209790a

1 files changed, 1 insertions, 5 deletions

diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 29d04a0cba..e3141baef0 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -631,7 +631,6 @@ private:
     std::atomic<bool> fScanningWallet{false}; // controlled by WalletRescanReserver
     std::atomic<int64_t> m_scanning_start{0};
     std::atomic<double> m_scanning_progress{0};
-    std::mutex mutexScanning;
     friend class WalletRescanReserver;
 
     //! the current wallet version: clients below this version are not able to load the wallet
@@ -1287,13 +1286,11 @@ public:
     bool reserve()
     {
         assert(!m_could_reserve);
-        std::lock_guard<std::mutex> lock(m_wallet.mutexScanning);
-        if (m_wallet.fScanningWallet) {
+        if (m_wallet.fScanningWallet.exchange(true)) {
             return false;
         }
         m_wallet.m_scanning_start = GetTimeMillis();
         m_wallet.m_scanning_progress = 0;
-        m_wallet.fScanningWallet = true;
         m_could_reserve = true;
         return true;
     }
@@ -1305,7 +1302,6 @@ public:
 
     ~WalletRescanReserver()
     {
-        std::lock_guard<std::mutex> lock(m_wallet.mutexScanning);
         if (m_could_reserve) {
             m_wallet.fScanningWallet = false;
         }