While debugging my massively multithreaded C++ application I would notice times where the application would seem to pause for a few moments. During one of these pauses I halted the application and attached to it with the debugger (GDB). From within GDB I listed (info threads), switched to (thread ) and looked at the stack (bt) of each thread running. I saw something surprising and very telling. Nearly every single thread that was supposed to be performing work was actually blocked on a mutex inside of either malloc or free.
I recently had the need to be able to query the WMI via WQL (which are very fascinating and helpful technologies, actually) from C++. WQL essentially provides an SQL interface for querying system properties of a running computer.
We’ve covered the “Assembly Language”, “C” and “C++” of the C++ threading world, and now we are going to try and move beyond that.
If boost::threads represent the C of multithreaded programming, then RAII and automatically managed threads represent the C++ of multithreaded programming. In the last article we promised that using more RAII would allow us to get this code even smaller and better to manage. Here is the result of that:
Understanding RAII is critical to understanding good C++ design.
