QProgressDialog or MainWindow with table Crashes when using with MultiThread

Maaz Momin

@jsulm I have updated StackTrace.

@J-Hilk As you can the parenting is already done in start processing function. Edit: Also in constructor i have initialized it to NULL

jsulm

@Maaz-Momin Please post whole stack trace (what you posted is cut at the bottom).

Maaz Momin

@jsulm The stacktrace seems to be almost 1000 table lines. Won't be able to post that many screenshots. Are you looking for something in particular?

dheerendra

If I look at your program this is what I understood.

There is only one progress Dialog created in mainWindow
You are creating the multiple Worker object & each running in different threads.
You have connected each of those worker object signals to progress dialog & vice/versa

Now

Can you show me how are you connecting progress value from worker to progress dialog ? Are you making any direct connection to update the progress ?
Are you calling setValue of progressdialog from any of the worker threads ?

Maaz Momin

@dheerendra

Q) Can you show me how are you connecting progress value from worker to progress dialog ? Are you making any direct connection to update the progress ? Are you calling setValue of progressdialog from any of the worker threads ?

Ans) No i am not connecting Worker to Progress. I wait for Worker to finish and trigger MainWindow's onProcessingFinished() slot. From this slot I call progressDialog ->setValue.

Maaz Momin

@jsulm @J-Hilk @dheerendra I just saw that i am also getting this error message in Issue panel.

"f:\dd\vctools\crt\vcstartup\src\misc\i386\chkstk.asm:99: error: Debugger encountered an exception: Exception at 0x625ab439, code: 0xc00000fd: stack_overflow, flags=0x0 (first chance)"

dheerendra

Debugger & trace is the only choice to find the issue. Since code is with you, only you can troubleshoot better. From our side it is only guess work. However some inputs from my side.

I'm seeing the stack_overflow. Is there any method getting called recursively ?
You are doing the foreach. How many worker threads you are creating ?
You are doing the moveToThread of worker. Does worker has any children objects ?
Just to rule out that issue is happening from ProgressBar, we can remove everything insid onProcessingFinished(). Just have debug statement. Just see how it behaves.
We can restrict the number of threads to just one, see how it behaves.

Please note that above are some hints for moving forward & not sure shot for troubleshooting.

Tools like WinDBG should clearly point out the issue.

kshegunov

@Maaz-Momin said in QProgressDialog or MainWindow with table Crashes when using with MultiThread:

@jsulm @J-Hilk @dheerendra I just saw that i am also getting this error message in Issue panel.

"f:\dd\vctools\crt\vcstartup\src\misc\i386\chkstk.asm:99: error: Debugger encountered an exception: Exception at 0x625ab439, code: 0xc00000fd: stack_overflow, flags=0x0 (first chance)"

Which is what I'd've guessed from this:

@jsulm The stacktrace seems to be almost 1000 table lines. Won't be able to post that many screenshots. Are you looking for something in particular?

Look over your code (and trace). There's probably a signal that's emitted secondary to a slot which is triggered by the same signal. I don't believe this to be a threading issue per se.

Maaz Momin

I traced over my code and but find any signal-slot recursive but i guess I understood the reason as the error suggest it's stack_overflow.

I am trying to read all the files in a folder(recursive) and process the files. My logic was to create each thread with total file size of 50KB.

but when I try this on a large folder say around (3.5MB and above) then only the program crashes.

My Log: '44' Batch(Thread) created for '390' files with total file size 3501128 bytes.

@SGaist @aha_1980 @mrjj @jsulm @J-Hilk @dheerendra @kshegunov Can you guys advise on how to handle Multiple-File reading and processing in MultiThread.

Maaz Momin

I found a way how I can work with this. The anwser is QThread::idealThreadCount. Thank you for your help.