multithreaded reeading and writing from buffer

The last years, 99% of my time I'm doing java so my C++ skills are well, erm, lets's say a bit at a low level.
But I'm having a bit of a problem.
I have a buffer that is accessed by two threads.
One for reading and one for writing to the buffer (a vector).
I'm pretty sure that I never write outside the memory allocated by the buffer.
Due to performance issues we tryed removing 2 mutex locks and that worked CPU usage droped with 50%. We made the methods where we removed the mutex locks a bit smarter so we first check if we can safely read or not.
That code isn't 100% safe because things can still go wrong between the check and the actual read.

Now, about 2 or 3 times a day, we get a blue screen on Win XP and immediately after a reset of windows.
Can this be the result of a push and pop on the same address?
As far as I know, if I try to write beyond my allocated memory I would get an access violation message but windows wouldn't reset. Is this the same with reading and writing to the same address?

I analysed the mini dumps from windows but that didn't give me any usefull information.

I haven't been able to simulate it on the development machine with debuging capabilities nor am I allowed post any code.
I also ran it with the ntsd but it hasn't crashed yet.

Could the windows crash be related to our program or can it be a hardware fault (like a heat problem)?


Thanks

Maes

I doubt you're causing the blue screen with that program unless your code is part of a driver (in which case unsafe thread code is a really baaaaaaaaad idea), or something else of that nature.

Windows NT based systems, such as XP, are pretty stable and don't usually blue screen unless there is a driver problem or something hardware related.

I agree, it's very unlikely that you will crash the system with a user-mode application (unless you are talking to a borken driver of course).

What is the bluescreen error you get?

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Mats

Quote:

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Originally Posted by maes

Could the windows crash be related to our program or can it be a hardware fault (like a heat problem)?

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Unlikely, since the problem only appeared once you changed your code. You might spend all week speculating why Windows crashes, but that's probably not a good use of your time since you might find another box where it doesn't crash. Just fix the code and chalk it up to "Who knows with Windows."

Quote:

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Originally Posted by matsp

I agree, it's very unlikely that you will crash the system with a user-mode application (unless you are talking to a borken driver of course).

What is the bluescreen error you get?

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Mats

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The blue screen disapears to quickly the computer resets immediatly after.
But I think you're all right. Last night I had the original program running and it still did a reboot.
So I doubt it will be a bug in our program.

Thanks for the help,

Maes

if i do not remember wrong you can download the tweakui utility from microsoft and disable the immediate reboot with it. then you are able to read the blue screen message.

Quote:

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Originally Posted by pheres

if i do not remember wrong you can download the tweakui utility from microsoft and disable the immediate reboot with it. then you are able to read the blue screen message.

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Yes - in fact, it doesn't take a TweakUI either - just go to Control-Panel->System->Advanced and unclick "Automatically reboot" - or if you have a minidump, you should be able to see the fault that caused the dump.

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Mats