How to find out where a thread lock happend?
- by SchlaWiener
One of our company's Windows Forms application had a strange problem for several month.
The app worked very reliable for most of our customers but on some PC's (mostly with a wireless lan connection) the app sometimes just didn't respond anymore. (You click on the UI and windows ask you to wait or kill the app).
I wasn't able to track down the problem for a long time but now I figured out what happend.
The app had this line of code
// don't blame me for this. Wasn't my code :D
Control.CheckForIllegalCrossThreadCalls = false
and used some background threads to modify the controls.
No I found a way to reproduce the application stopping responding bug on my dev machine and tracked it down to a line where I actually used Invoke() to run a task in the main thread.
Me.Invoke(MyDelegate, arg1, arg2)
Obviously there was a thread lock somewhere.
After removing the
Control.CheckForIllegalCrossThreadCalls = false
statement and refactoring the whole programm to use Invoke() if modifying a control from a background thread, the problem is (hopefully) gone.
However, I am wondering if there is a way to find such bugs without debugging every line of code (Even if I break into debugger after the app stops responding I can't tell what happend last, because the IDE didn't jump to the Invoke() statement)
In other words:
If my apps hangs how can I figure out
which line of code has been executed
last?
Maybe even on the customers PC.
I know VS2010 offers some backwards debugging feature, maybe that would be a solution, but currently I am using VS2008.
