diff --git a/src/Server/TCPHandler.cpp b/src/Server/TCPHandler.cpp index 07366d7cc07..2a2e2e22538 100644 --- a/src/Server/TCPHandler.cpp +++ b/src/Server/TCPHandler.cpp @@ -1,48 +1,48 @@ -#include -#include -#include #include #include #include #include -#include #include -#include -#include -#include -#include -#include -#include -#include -#include -#include +#include +#include +#include #include #include -#include -#include -#include -#include -#include +#include +#include +#include #include #include -#include -#include +#include +#include +#include +#include +#include +#include +#include #include #include #include +#include +#include +#include +#include #include -#include #include #include -#include -#include -#include -#include -#include -#include +#include +#include +#include +#include #include +#include +#include +#include +#include +#include +#include +#include #include -#include #include #include @@ -61,6 +61,8 @@ #include +#include + using namespace std::literals; using namespace DB; @@ -1036,6 +1038,17 @@ void TCPHandler::processOrdinaryQuery() PullingAsyncPipelineExecutor executor(pipeline); CurrentMetrics::Increment query_thread_metric_increment{CurrentMetrics::QueryThread}; + /// The following may happen: + /// * current thread is holding the lock + /// * because of the exception we unwind the stack and call the destructor of `executor` + /// * the destructor calls cancel() and waits for all query threads to finish + /// * at the same time one of the query threads is trying to acquire the lock, e.g. inside `merge_tree_read_task_callback` + /// * deadlock + SCOPE_EXIT({ + if (out_lock.owns_lock()) + out_lock.unlock(); + }); + Block block; while (executor.pull(block, interactive_delay / 1000)) { @@ -1079,8 +1092,7 @@ void TCPHandler::processOrdinaryQuery() } /// This lock wasn't acquired before and we make .lock() call here - /// so everything under this line is covered even together - /// with sendProgress() out of the scope + /// so everything under this line is covered. out_lock.lock(); /** If data has run out, we will send the profiling data and total values to @@ -1107,6 +1119,7 @@ void TCPHandler::processOrdinaryQuery() last_sent_snapshots.clear(); } + out_lock.lock(); sendProgress(); }