[routing] Fixed a data race in AltitudeLoader.

AltitudeLoader holds a FileReader of the altitudes section.
This reader, being a caching one, is not thread safe. However,
AltitudeLoader did not keep the MwmHandle from which it was
supposed to construct its reader, so the reader could be reused
(via MwmValue via MwmHandle) by another thread.

FeaturesRoadGraph tries to avoid this issue by keeping its
own cache of MwmHandles but it did not stop RoadGeometry
from bypassing this cache when creating its AltitudeLoader.

The question of whether we need to fix this other cache
and whether we need it at all is out of the scope of this CL.

indexer/altitude_loader.cpp

@@ -29,8 +29,14 @@ void LoadAndMap(size_t dataSize, ReaderSource<FilesContainerR::TReader> & src, T
 
 namespace feature
 {
-AltitudeLoader::AltitudeLoader(MwmValue const & mwmValue)
+AltitudeLoader::AltitudeLoader(Index const & index, MwmSet::MwmId const & mwmId)
+  : m_handle(index.GetMwmHandleById(mwmId))
 {
+  if (!m_handle.IsAlive())
+    return;
+
+  auto const & mwmValue = *m_handle.GetValue<MwmValue>();
+
   m_countryFileName = mwmValue.GetCountryFileName();
 
   if (mwmValue.GetHeader().GetFormat() < version::Format::v8)

indexer/altitude_loader.hpp

@@ -1,6 +1,7 @@
 #pragma once
 #include "indexer/feature_altitude.hpp"
 #include "indexer/index.hpp"
+#include "indexer/mwm_set.hpp"
 
 #include "coding/memory_region.hpp"
 
@@ -15,7 +16,7 @@ namespace feature
 class AltitudeLoader
 {
 public:
-  explicit AltitudeLoader(MwmValue const & mwmValue);
+  explicit AltitudeLoader(Index const & index, MwmSet::MwmId const & mwmId);
 
   /// \returns altitude of feature with |featureId|. All items of the returned vector are valid
   /// or the returned vector is empty.
@@ -36,5 +37,6 @@ private:
   map<uint32_t, TAltitudes> m_cache;
   AltitudeHeader m_header;
   string m_countryFileName;
+  MwmSet::MwmHandle m_handle;
 };
 }  // namespace feature

routing/features_road_graph.cpp

@@ -27,12 +27,13 @@ double constexpr kMwmCrossingNodeEqualityRadiusMeters = 100.0;
 
 }  // namespace
 
-FeaturesRoadGraph::Value::Value(MwmSet::MwmHandle handle) : m_mwmHandle(move(handle))
+FeaturesRoadGraph::Value::Value(Index const & index, MwmSet::MwmHandle handle)
+  : m_mwmHandle(move(handle))
 {
   if (!m_mwmHandle.IsAlive())
     return;
 
-  m_altitudeLoader = make_unique<feature::AltitudeLoader>(*m_mwmHandle.GetValue<MwmValue>());
+  m_altitudeLoader = make_unique<feature::AltitudeLoader>(index, m_mwmHandle.GetId());
 }
 
 FeaturesRoadGraph::CrossCountryVehicleModel::CrossCountryVehicleModel(
@@ -331,7 +332,7 @@ FeaturesRoadGraph::Value const & FeaturesRoadGraph::LockMwm(MwmSet::MwmId const
   if (itr != m_mwmLocks.end())
     return itr->second;
 
-  return m_mwmLocks.insert(make_pair(move(mwmId), Value(m_index.GetMwmHandleById(mwmId))))
+  return m_mwmLocks.insert(make_pair(move(mwmId), Value(m_index, m_index.GetMwmHandleById(mwmId))))
       .first->second;
 }
 }  // namespace routing

routing/features_road_graph.hpp

@@ -6,6 +6,7 @@
 
 #include "indexer/altitude_loader.hpp"
 #include "indexer/feature_data.hpp"
+#include "indexer/index.hpp"
 #include "indexer/mwm_set.hpp"
 
 #include "geometry/point2d.hpp"
@@ -87,7 +88,7 @@ private:
   struct Value
   {
     Value() = default;
-    explicit Value(MwmSet::MwmHandle handle);
+    explicit Value(Index const & index, MwmSet::MwmHandle handle);
 
     bool IsAlive() const { return m_mwmHandle.IsAlive(); }
 

routing/geometry.cpp

@@ -38,7 +38,7 @@ GeometryLoaderImpl::GeometryLoaderImpl(Index const & index, MwmSet::MwmHandle co
   : m_vehicleModel(move(vehicleModel))
   , m_guard(index, handle.GetId())
   , m_country(handle.GetInfo()->GetCountryName())
-  , m_altitudeLoader(*handle.GetValue<MwmValue>())
+  , m_altitudeLoader(index, handle.GetId())
   , m_loadAltitudes(loadAltitudes)
 {
   CHECK(handle.IsAlive(), ());