Merge #14993: rpc: Fix data race (UB) in InterruptRPC()

6c10037f72 rpc: Fix data race (UB) in InterruptRPC() (practicalswift)

Pull request description:

  Fix data race (UB) in `InterruptRPC()`.

  Before:

  ```
  $ ./configure --with-sanitizers=thread
  $ make
  $ test/functional/test_runner.py feature_shutdown.py
  …
  SUMMARY: ThreadSanitizer: data race rpc/server.cpp:314 in InterruptRPC()
  …
  ALL                 | ✖ Failed  | 2 s (accumulated)
  ```

  After:

  ```
  $ ./configure --with-sanitizers=thread
  $ make
  $ test/functional/test_runner.py feature_shutdown.py
  …
  ALL                 | ✓ Passed  | 3 s (accumulated)
  ```

Tree-SHA512: b139ca1a0480258f8caa7730cabd7783a821d906630f51487750a6b15b7842675ed679747e1ff1bdade77d248807e9d77bae7bb88da54d1df84a179cd9b9b987

src/rpc/server.cpp

@@ -24,7 +24,7 @@
 #include <unordered_map>
 
 static CCriticalSection cs_rpcWarmup;
-static bool fRPCRunning = false;
+static std::atomic<bool> g_rpc_running{false};
 static bool fRPCInWarmup GUARDED_BY(cs_rpcWarmup) = true;
 static std::string rpcWarmupStatus GUARDED_BY(cs_rpcWarmup) = "RPC server started";
 /* Timer-creating functions */
@@ -303,7 +303,7 @@ bool CRPCTable::appendCommand(const std::string& name, const CRPCCommand* pcmd)
 void StartRPC()
 {
     LogPrint(BCLog::RPC, "Starting RPC\n");
-    fRPCRunning = true;
+    g_rpc_running = true;
     g_rpcSignals.Started();
 }
 
@@ -311,7 +311,7 @@ void InterruptRPC()
 {
     LogPrint(BCLog::RPC, "Interrupting RPC\n");
     // Interrupt e.g. running longpolls
-    fRPCRunning = false;
+    g_rpc_running = false;
 }
 
 void StopRPC()
@@ -324,7 +324,7 @@ void StopRPC()
 
 bool IsRPCRunning()
 {
-    return fRPCRunning;
+    return g_rpc_running;
 }
 
 void SetRPCWarmupStatus(const std::string& newStatus)

test/sanitizer_suppressions/tsan

@@ -7,9 +7,6 @@ deadlock:WalletBatch
 # Intentional deadlock in tests
 deadlock:TestPotentialDeadLockDetected
 
-# fRPCRunning race
-race:InterruptRPC
-
 # Wildcard for all gui tests, should be replaced with non-wildcard suppressions
 race:src/qt/test/*
 deadlock:src/qt/test/*