CreateProcess and Parent Threads

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I'm having a problem with my dongle heartbeat. We have been using a timer to send a heartbeat to our dongle to keep the license alive. However, if one of our processor-intensive subprocesses takes longer than the dongle license timeout, the application needs to be restarted.

The subprocess in question involves running a third party console app and redirecting its output to our log file. This sub-app is launched using ::CreateProcess. Since WM_TIMER is a low priority, the heartbeat timer messages get shunted off and the license expires.

So I thought what was necessary was to put the heart-beat timer into its own thread. I did this, but the ::CreateProcess appears to block all threads in the parent app.

I don't want to run the sub-process asynchronously, so how do I get my heart-beat thread to keep running at the same time?

Additional:
My timer thread is essentially this:
Threads And Timers[^]

And I just noticed that my console redirection class (optionally) does a WaitForSingleObject on the created process, which is presumably what blocks the parent threads. Essentially, I need my parent app to continue with its 'background' threads while waiting for the spawned process to finish (without using WaitForSingleObject?).

Posted 25-Jul-12 18:35pm

Kyudos

Updated 16-Jun-17 23:34pm

v2

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Jochen Arndt 26-Jul-12 3:03am

CreateProcess returns immediately and would not block. So the problem must be somewhere else.

Did you still use WM_TIMER in your new heart-beat thread? If so, use WaitForSingleObject with the heart-beat time out value and a kill event handle set upon program exit. Then the heart-beat timer does not need message handling. You may also set the priority of the heart-beat thread above the priority of your main application.

pasztorpisti 26-Jul-12 4:35am

The problem can also be in the process being launched. I observed that some porocesses work so intensively (especially some antivirus software in nightly mode) that you feel it on the user interface even on an intel i7.

Code-o-mat 26-Jul-12 4:54am

Can you show us what that thread does? You could use the "improve question" link under your post to add some relevant code sniplets, don't forget to tag them accordingly.

Jochen Arndt 26-Jul-12 6:54am

To your update:
The timer thread you are using is not the best choice because it is still using the Windows Timers.
My suggestion:
- Create a worker thread and a terminate event
- In the worker thread use WaitForSingleObject with the terminate event handle and your heart beat timeout inside a while loop.
- Upon terminate event, leave the loop and return from the thread.
- Upon time out, execute your heart beat function.
- Upon program exit, fire the terminate event.

Optional set the thread priority one above the main app priority (see AfxBeginThread). Your external process will probably have the same priority as your main app. Then the heart beat should work (if not delayed by heavy system load with higher priorities).

enhzflep 26-Jul-12 10:39am

If this was an answer it could be up-voted...

Jochen Arndt 26-Jul-12 11:00am

Thank you. I'm still not sure if it solves the problem, but I think so. If there's some positive feedback, I may post it as solution.

Kyudos 26-Jul-12 20:04pm

Jochen - this works great thanks - I'd mark it as the answer:)

Jochen Arndt 27-Jul-12 10:29am

Thank you for your feedback. I have added an solution, so the case may be closed.

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Jochen Arndt · Accepted Answer · 2012-07-27T04:29:00

From the updated question and the comments, this seems to solve the problem:

Using the Windows timers is often not the best choice. For periodic actions that are hardware related and/or sensitive to system load, a worker thread may be a better solution:

Create a worker thread and a terminate event.
In the worker thread use WaitForSingleObject() with the terminate event handle and your heart beat timeout inside a while loop.
Upon the terminate event, leave the loop and return from the thread.
Upon time out, execute your heart beat function.
Upon program exit, fire the terminate event.

Optional set the thread priority one above the main app priority (see AfxBeginThread). Your external process will probably have the same priority as your main app. Then the heart beat should work (if not delayed by heavy system load with higher priorities).