fees: make the class FeeFilterRounder thread-safe

So that its methods can be called concurrently by different threads on
the same object. Currently it has just one method (`round()`).

Co-authored-by: Hennadii Stepanov <32963518+hebasto@users.noreply.github.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/src/policy/fees.h b/src/policy/fees.h
index 6e25bb42b8..c7fa1a0b77 100644
--- a/src/policy/fees.h
+++ b/src/policy/fees.h
@@ -299,12 +299,13 @@ public:
     /** Create new FeeFilterRounder */
     explicit FeeFilterRounder(const CFeeRate& minIncrementalFee);
 
-    /** Quantize a minimum fee for privacy purpose before broadcast. Not thread-safe due to use of FastRandomContext */
+    /** Quantize a minimum fee for privacy purpose before broadcast. */
     CAmount round(CAmount currentMinFee);
 
 private:
     std::set<double> feeset;
-    FastRandomContext insecure_rand;
+    Mutex m_insecure_rand_mutex;
+    FastRandomContext insecure_rand GUARDED_BY(m_insecure_rand_mutex);
 };
 
 #endif // BITCOIN_POLICY_FEES_H