Episode

Defrag Tools: #24 - WinDbg - Critical Sections

Defrag Tools

In this episode of Defrag Tools, Andrew Richards, Chad Beeder and Larry Larsen continue looking at the Debugging Tools for Windows (in particular WinDbg). WinDbg is a debugger that supports user mode debugging of a process, or kernel mode debugging of a computer.

This installment goes over the commands used to diagnose a Critical Section hang in a user mode application. We start with an overview of the four synchronization primitives and then delve deep in to temporary hangs, orphaned Critical Sections and deadlocks. We use these commands:

  • ~*k
  • ~*kv
  • ~
  • ~~[TID]s
  • !cs
  • !cs
  • !locks

Make sure you watch Defrag Tools Episode #1 and Defrag Tools Episode #23 for instructions on how to get the Debugging Tools for Windows and how to set the required environment variables for symbols and source code resolution.

Resources:
Critical Section Objects

Timeline: [01:00] - Hang types - CPU Looping, Temporary Hangs and Permanent Hangs
[02:00] - Synchronization Objects - Event, Semaphore, Mutex, Critical Section
[06:54] - Critical Sections
[11:45] - Debugging a Hang
[28:08] - Debugging an Orphan
[32:40] - Debugging a Deadlock