Download - Advanced Debugging with WinDbg and SOS

Sasha Goldshtein

CTOSela Group

@goldshtnblog.sashag.net

Advanced Debugging with

WinDbg and SOS

www.devconnections.com

ADVANCED DEBUGGING WITH WINDBG AND SOS

AN HOUR FROM NOW,YOU’LL KNOW HOW TO:

Capture crash and hang dumps Pinpoint basic crash causes from

dumps Inspect heap objects and graphs to find

memory leaks Identify deadlocked threads



DUMPS 101



A DUMP IS A SNAPSHOT OF A RUNNING PROCESS. YOU CAN

SAVE IT, MOVE IT AROUND, AND ANALYZE IT LATER. YOU CAN’T

“DEBUG” IT.



TWO TYPES OF DUMPS:

Crash Dump The program crashed

Hang Dump The program didn’t crash

Yet



SYSINTERNALS PROCDUMP: TAKE DUMPS EASILY, ANYWHERE, AND

WITH NO PUN INTENDED.

Procdump -ma -e MyApp.exeProcdump -h -x C:\temp\myapp.exeProcdump -c 90 -n 3 -s 5 MyApp.exeProcdump -e 1 1234



CRASH ROOT CAUSE FROM A DUMP



DRAG AND DROP A DUMP FILE INTO VISUAL STUDIO. CLICK THE

GREEN BUTTON. VOILA, IT WORKS.*

* NITPICKER’S CORNER: YOU NEED SYMBOLS AND SOURCES TO BE LINED UP PROPERLY.



“

”

YOU WILL INSTALL VISUAL STUDIO ON MY BOXEN OVER MY DEAD BODY. GOOD DAY.

I SAID “GOOD DAY”.

Joe the IT Admin



10

ENTER:

WinDbg Lightweight GUI debugger

Super-scriptable

Super-extensible

Knows nothing about .NET

SOS WinDbg extension for .NET

Ships with .NET Framework

Or on the symbol server*

Knows all about .NET

* As of CLR 4.0, for GDR versions



TAKE 2:

Drag and drop a dump file into WinDbg. Hmm. Now what?

!analyze -v !PrintException!CLRStack .load sosex!mk !mdt

.for (r $t0=@ebp; poi(@$t0)!=0; r $t0=poi(@$t0)) { !mln poi(@$t0+4) }



MEMORY LEAKS: THE EASY WAY

Not in this talk. Shell out $500 for a decent memory profiler.



MEMORY LEAKS: THE HARD WAY



WHAT WE NEED:

1. A list of all heap objects

2. A diff of heap objects between dumps

3. Why these heap objects won’t go away

!dumpheap -stat !objsize!gcroot !refs



DEADLOCKS



WHAT WE NEED:

1. What is thread X waiting for

2. (Suppose it’s sync object Y)

3. Which thread owns sync object Y

!syncblk !mwaits!mlocks !dlk



ADDITIONAL REFERENCES



18

THANK YOU!

Sasha Goldshtein@goldshtn

[email protected]

Download - Advanced Debugging with WinDbg and SOS

Top Related