Race condition in CScheduler::serviceQueue #6394

CScheduler::serviceQueue has the following code:

+            lock.unlock();
+            f();
+            lock.lock();
+        } catch (...) {
+            --nThreadsServicingQueue;
+            throw;
+        }

In case f throws the statement --nThreadsServicingQueue; will run while not protected by the lock. This is a race condition and UB.

Good catch.