Replace boost::shared_mutex and shared_lock with their std:: equivale…

…nt in rwcollection.h

Summary:
This is possible since we use C++17.

Note that core raised some concerns about std::shared_mutex because of a couple bad glibc bugs that could cause deadlocks (bitcoin/bitcoin#16684 (comment)), so I checked that our release building version (Debian 10) was patched. As far as I can tell all our officially supported Linux are safe (all the ones we provide packages for). The only major distro I don't know for sure is CentOS 8, which runs a patched 2.28 version.

Ref T1634.

Test Plan:
  ninja all check-all
  ./contrib/teamcity/build-configurations.py build-tsan

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Maniphest Tasks: T1634

Differential Revision: https://reviews.bitcoinabc.org/D9877

src/rwcollection.h

@@ -8,10 +8,9 @@
 #include <threadsafety.h>
 
 #include <boost/range/iterator.hpp>
-#include <boost/thread/locks.hpp>
-#include <boost/thread/shared_mutex.hpp>
 
 #include <iterator>
+#include <shared_mutex>
 #include <type_traits>
 #include <utility>
 
@@ -67,22 +66,21 @@ template <typename T, typename L> class RWCollectionView {
 template <typename T> class RWCollection {
 private:
     T collection;
-    mutable boost::shared_mutex rwmutex;
+    mutable std::shared_mutex rwmutex;
 
 public:
     RWCollection() : collection() {}
 
     using ReadView =
-        RWCollectionView<const T, boost::shared_lock<boost::shared_mutex>>;
+        RWCollectionView<const T, std::shared_lock<std::shared_mutex>>;
     ReadView getReadView() const {
-        return ReadView(boost::shared_lock<boost::shared_mutex>(rwmutex),
+        return ReadView(std::shared_lock<std::shared_mutex>(rwmutex),
                         collection);
     }
 
-    using WriteView =
-        RWCollectionView<T, boost::unique_lock<boost::shared_mutex>>;
+    using WriteView = RWCollectionView<T, std::unique_lock<std::shared_mutex>>;
     WriteView getWriteView() {
-        return WriteView(boost::unique_lock<boost::shared_mutex>(rwmutex),
+        return WriteView(std::unique_lock<std::shared_mutex>(rwmutex),
                          collection);
     }
 };

test/lint/lint-boost-dependencies.sh

@@ -31,7 +31,6 @@ EXPECTED_BOOST_INCLUDES=(
     boost/signals2/signal.hpp
     boost/test/unit_test.hpp
     boost/thread/condition_variable.hpp
-    boost/thread/locks.hpp
     boost/thread/mutex.hpp
     boost/thread/shared_mutex.hpp
     boost/thread/thread.hpp