sm: networkmanager: fix DNSServer host map data race - #293
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Launcher::StopNetworks fans out per-instance network teardown across a thread pool. Instances sharing a network resolve to the same DNSServer, and NetworkManager::DeleteInstanceNetworkConfig released its lock before calling DNSServer::RemoveHost, so RemoveHost/AddHost mutated the unsynchronized mHosts map concurrently from multiple pool threads. This corrupted the map's internal red-black tree, observed on target as a worker thread spinning forever inside std::_Rb_tree_increment from WriteHostsFile, which made StopNetworks' pool wait hang forever and looked like a service deadlock. Add a mutex to DNSServer guarding mHosts across AddHost, RemoveHost and LoadHostsFile. Signed-off-by: Oleksandr Grytsov <oleksandr_grytsov@epam.com>
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Launcher::StopNetworks fans out per-instance network teardown across a thread pool. Instances sharing a network resolve to the same DNSServer, and NetworkManager::DeleteInstanceNetworkConfig released its lock before calling DNSServer::RemoveHost, so RemoveHost/AddHost mutated the unsynchronized mHosts map concurrently from multiple pool threads.
This corrupted the map's internal red-black tree, observed on target as a worker thread spinning forever inside std::_Rb_tree_increment from WriteHostsFile, which made StopNetworks' pool wait hang forever and looked like a service deadlock.
Add a mutex to DNSServer guarding mHosts across AddHost, RemoveHost and LoadHostsFile.