shm: ResetContent(): reset data after recreating the metadata

fairmq/shmem/Monitor.cxx

@@ -574,7 +574,7 @@ std::vector<std::pair<std::string, bool>> Monitor::Cleanup(const ShmId& shmIdT,
 
     string managementSegmentName("fmq_" + shmId + "_mng");
     try {
-        bipc::managed_shared_memory managementSegment(bipc::open_only, managementSegmentName.c_str());
+        bipc::managed_shared_memory managementSegment(bipc::open_read_only, managementSegmentName.c_str());
 
         Uint16RegionInfoHashMap* shmRegions = managementSegment.find<Uint16RegionInfoHashMap>(bipc::unique_instance).first;
         if (shmRegions) {
@@ -660,27 +660,35 @@ void Monitor::ResetContent(const ShmId& shmIdT, bool verbose /* = true */)
         managed_shared_memory managementSegment(open_only, managementSegmentName.c_str());
 
         Uint16SegmentInfoHashMap* segmentInfos = managementSegment.find<Uint16SegmentInfoHashMap>(unique_instance).first;
-        for (const auto& s : *segmentInfos) {
-            if (verbose) {
-                cout << "Resetting content of segment '" << "fmq_" << shmId << "_m_" << s.first << "'..." << endl;
-            }
-            try {
-                if (s.second.fAllocationAlgorithm == AllocationAlgorithm::rbtree_best_fit) {
-                    RBTreeBestFitSegment segment(open_only, std::string("fmq_" + shmId + "_m_" + to_string(s.first)).c_str());
-                    void* ptr = segment.get_segment_manager();
-                    size_t size = segment.get_segment_manager()->get_size();
-                    new(ptr) segment_manager<char, rbtree_best_fit<mutex_family, offset_ptr<void>>, null_index>(size);
-                } else {
-                    SimpleSeqFitSegment segment(open_only, std::string("fmq_" + shmId + "_m_" + to_string(s.first)).c_str());
-                    void* ptr = segment.get_segment_manager();
-                    size_t size = segment.get_segment_manager()->get_size();
-                    new(ptr) segment_manager<char, simple_seq_fit<mutex_family, offset_ptr<void>>, null_index>(size);
-                }
-            } catch (bie& e) {
+        if (segmentInfos) {
+            cout << "Found info for " << segmentInfos->size() << " managed segments" << endl;
+            for (const auto& s : *segmentInfos) {
                 if (verbose) {
-                    cout << "Error resetting content of segment '" << std::string("fmq_" + shmId + "_m_" + to_string(s.first)) << "': " << e.what() << endl;
+                    cout << "Resetting content of segment '" << "fmq_" << shmId << "_m_" << s.first << "'..." << endl;
+                }
+                try {
+                    if (s.second.fAllocationAlgorithm == AllocationAlgorithm::rbtree_best_fit) {
+                        RBTreeBestFitSegment segment(open_only, std::string("fmq_" + shmId + "_m_" + to_string(s.first)).c_str());
+                        void* ptr = segment.get_segment_manager();
+                        size_t size = segment.get_segment_manager()->get_size();
+                        new(ptr) segment_manager<char, rbtree_best_fit<mutex_family, offset_ptr<void>>, null_index>(size);
+                    } else {
+                        SimpleSeqFitSegment segment(open_only, std::string("fmq_" + shmId + "_m_" + to_string(s.first)).c_str());
+                        void* ptr = segment.get_segment_manager();
+                        size_t size = segment.get_segment_manager()->get_size();
+                        new(ptr) segment_manager<char, simple_seq_fit<mutex_family, offset_ptr<void>>, null_index>(size);
+                    }
+                    if (verbose) {
+                        cout << "Done." << endl;
+                    }
+                } catch (bie& e) {
+                    if (verbose) {
+                        cout << "Error resetting content of segment '" << std::string("fmq_" + shmId + "_m_" + to_string(s.first)) << "': " << e.what() << endl;
+                    }
                 }
             }
+        } else {
+            cout << "Found management segment, but cannot locate segment info, something went wrong..." << endl;
         }
 
         Uint16RegionInfoHashMap* shmRegions = managementSegment.find<Uint16RegionInfoHashMap>(bipc::unique_instance).first;
@@ -717,13 +725,15 @@ void Monitor::ResetContent(const ShmId& shmIdT, const std::vector<SegmentConfig>
 
     std::string shmId = shmIdT.shmId;
     std::string managementSegmentName("fmq_" + shmId + "_mng");
-    // reset managed segments
-    ResetContent(shmIdT, verbose);
     // delete management segment
+    cout << "deleting management segment" << endl;
     Remove<bipc::shared_memory_object>(managementSegmentName, verbose);
     // recreate management segment
+    cout << "recreating management segment..." << endl;
     managed_shared_memory mngSegment(create_only, managementSegmentName.c_str(), kManagementSegmentSize);
+    cout << "done." << endl;
     // fill management segment with segment & region infos
+    cout << "filling management segment with managed segment configs..." << endl;
     for (const auto& s : segmentCfgs) {
         if (s.allocationAlgorithm == "rbtree_best_fit") {
             Segment::Register(shmId, s.id, AllocationAlgorithm::rbtree_best_fit);
@@ -734,9 +744,14 @@ void Monitor::ResetContent(const ShmId& shmIdT, const std::vector<SegmentConfig>
             throw MonitorError("Unknown allocation algorithm provided: " + s.allocationAlgorithm);
         }
     }
+    cout << "done." << endl;
+    cout << "filling management segment with unmanaged region configs..." << endl;
     for (const auto& r : regionCfgs) {
         fair::mq::shmem::UnmanagedRegion::Register(shmId, r);
     }
+    cout << "done." << endl;
+    // reset managed segments
+    ResetContent(shmIdT, verbose);
 }
 
 void Monitor::ResetContent(const SessionId& sessionId, const std::vector<SegmentConfig>& segmentCfgs, const std::vector<RegionConfig>& regionCfgs, bool verbose /* = true */)