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, 9 insertions, 13 deletions

diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 7d43de6646..4eb47d7b15 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -52,7 +52,7 @@ struct CUpdatedBlock
 
 static Mutex cs_blockchange;
 static std::condition_variable cond_blockchange;
-static CUpdatedBlock latestblock;
+static CUpdatedBlock latestblock GUARDED_BY(cs_blockchange);
 
 NodeContext& EnsureNodeContext(const util::Ref& context)
 {
@@ -223,7 +223,7 @@ static UniValue getbestblockhash(const JSONRPCRequest& request)
 void RPCNotifyBlockChange(const CBlockIndex* pindex)
 {
     if(pindex) {
-        std::lock_guard<std::mutex> lock(cs_blockchange);
+        LOCK(cs_blockchange);
         latestblock.hash = pindex->GetBlockHash();
         latestblock.height = pindex->nHeight;
     }
@@ -258,9 +258,9 @@ static UniValue waitfornewblock(const JSONRPCRequest& request)
         WAIT_LOCK(cs_blockchange, lock);
         block = latestblock;
         if(timeout)
-            cond_blockchange.wait_for(lock, std::chrono::milliseconds(timeout), [&block]{return latestblock.height != block.height || latestblock.hash != block.hash || !IsRPCRunning(); });
+            cond_blockchange.wait_for(lock, std::chrono::milliseconds(timeout), [&block]() EXCLUSIVE_LOCKS_REQUIRED(cs_blockchange) {return latestblock.height != block.height || latestblock.hash != block.hash || !IsRPCRunning(); });
         else
-            cond_blockchange.wait(lock, [&block]{return latestblock.height != block.height || latestblock.hash != block.hash || !IsRPCRunning(); });
+            cond_blockchange.wait(lock, [&block]() EXCLUSIVE_LOCKS_REQUIRED(cs_blockchange) {return latestblock.height != block.height || latestblock.hash != block.hash || !IsRPCRunning(); });
         block = latestblock;
     }
     UniValue ret(UniValue::VOBJ);
@@ -300,9 +300,9 @@ static UniValue waitforblock(const JSONRPCRequest& request)
     {
         WAIT_LOCK(cs_blockchange, lock);
         if(timeout)
-            cond_blockchange.wait_for(lock, std::chrono::milliseconds(timeout), [&hash]{return latestblock.hash == hash || !IsRPCRunning();});
+            cond_blockchange.wait_for(lock, std::chrono::milliseconds(timeout), [&hash]() EXCLUSIVE_LOCKS_REQUIRED(cs_blockchange) {return latestblock.hash == hash || !IsRPCRunning();});
         else
-            cond_blockchange.wait(lock, [&hash]{return latestblock.hash == hash || !IsRPCRunning(); });
+            cond_blockchange.wait(lock, [&hash]() EXCLUSIVE_LOCKS_REQUIRED(cs_blockchange) {return latestblock.hash == hash || !IsRPCRunning(); });
         block = latestblock;
     }
 
@@ -344,9 +344,9 @@ static UniValue waitforblockheight(const JSONRPCRequest& request)
     {
         WAIT_LOCK(cs_blockchange, lock);
         if(timeout)
-            cond_blockchange.wait_for(lock, std::chrono::milliseconds(timeout), [&height]{return latestblock.height >= height || !IsRPCRunning();});
+            cond_blockchange.wait_for(lock, std::chrono::milliseconds(timeout), [&height]() EXCLUSIVE_LOCKS_REQUIRED(cs_blockchange) {return latestblock.height >= height || !IsRPCRunning();});
         else
-            cond_blockchange.wait(lock, [&height]{return latestblock.height >= height || !IsRPCRunning(); });
+            cond_blockchange.wait(lock, [&height]() EXCLUSIVE_LOCKS_REQUIRED(cs_blockchange) {return latestblock.height >= height || !IsRPCRunning(); });
         block = latestblock;
     }
     UniValue ret(UniValue::VOBJ);
@@ -1995,7 +1995,6 @@ bool FindScriptPubKey(std::atomic<int>& scan_progress, const std::atomic<bool>&
 }
 
 /** RAII object to prevent concurrency issue when scanning the txout set */
-static std::mutex g_utxosetscan;
 static std::atomic<int> g_scan_progress;
 static std::atomic<bool> g_scan_in_progress;
 static std::atomic<bool> g_should_abort_scan;
@@ -2008,18 +2007,15 @@ public:
 
     bool reserve() {
         CHECK_NONFATAL(!m_could_reserve);
-        std::lock_guard<std::mutex> lock(g_utxosetscan);
-        if (g_scan_in_progress) {
+        if (g_scan_in_progress.exchange(true)) {
             return false;
         }
-        g_scan_in_progress = true;
         m_could_reserve = true;
         return true;
     }
 
     ~CoinsViewScanReserver() {
         if (m_could_reserve) {
-            std::lock_guard<std::mutex> lock(g_utxosetscan);
             g_scan_in_progress = false;
         }
     }