GPU621/Sentinel

Multithreaded Application Debugging in Visual Studio

• The project is based on the material outlined in "Debug multithreaded applications in Visual Studio" section of MSDN documentation and other related MSDN documentation.

Group Members

1. Ekaterina Zaytseva
2. Mohammad Yasir
3. Natan Ross
4. eMail All

Introduction

Multithreaded applications debugging overview

Debugging is one of the crucial software development stages. While all of us know the importance and the basics of debugging in the Visual Studio, debugging the multithreaded applications is more complicated than that of the serial programs we were used to before. The first problem of the multithreaded debugging is keeping track of multiple threads instead of just one as we did with the serial programs. Secondly, having multiple threads introduces new kinds of bugs and issues that can seriously affect the output of the software. Such issues include race conditions and deadlocks. A race condition is the behavior of the system when the output is dependent on the sequence of other events or commands. It becomes a bug when the events are out of order (Race condition wiki). Deadlock is a situation when each member of the group (a group of threads in our case) is waiting for some other member to take action, it typically happens when mutual exclusion is executed incorrectly, and the lock on the resource cannot be released (Deadlock wiki).

Visual Studio tools for multithreaded debugging

Visual Studio provides the developers with a variety of tools to assist with the multithreaded application debugging based on the specifics of the implementation:

• Threads
  • Threads window - Allows to view and manipulate the threads, also provides partial call stack for each of the threads
  • Thread markers - Icon resembling two cloth threads indicating where a thread is stopped. Provides a DataTip containing the name and thread ID, as well as thread manipulation shortcut menu
  • Parallel Stacks window - Shows call stack information for all the threads in the program
  • Parallel Watch window - Tracks the values produced by the multithreaded expression
  • Debug Location toolbar - Allows to manipulate threads and processes
• Task parallelism
  • Parallel Stacks window (discussed above)
  • Parallel Watch window (discussed above)
  • Tasks window - Lists all the current parallel and scheduled tasks
• GPU threads
  • GPU Threads window - Allows to work with the GPU threads
• Processes
  • Attach to Process dialog box - Allows the developer to attach the VS debugger to the process, enables the process debugging
  • Processes window - Lists all the processes currently attached to the debugger
  • Debug Location toolbar (discussed above)

Basic Debugging Steps

1. Build in Debug mode
2. Double-check the outputs
3. Start where the bug is

How to Debug Multithreaded Application in VS

1. Tools in more detail (maybe show an example ourselves)
2. Walkthrough (workshop-style)