Hello,

I have a seemingly simple question which nevertheless is giving me headaches: I have a main thread which does nothing but [1] execute CheckSynchronize, then [2] check whether some other things have to be done as a result of the synchronization (and do those things if necessary), then go back to [1] (until some quit condition is met).

Now, instead of busy waiting in the main thread loop (even with a Sleep inserted), I'd rather have it idle wait until another thread needs to synchronize. Is that possible?

I have tested a solution which achieves what I want (main thread waits until some other thread wakes it) with a TEventObject, but that requires threads to explicitly post a specific event and breaks support for threads which simply expect CheckSynchronize to be called regularly.

I'd really appreciate any hints on this.

Cheers
Roland

Allow me to bump this. I'd appreciate any comments, even if it's "Why on earth do you want to do that!?" or something.

Thanks
Roland

Roland Schaefer wrote

Now, instead of busy waiting in the main thread loop (even with a Sleep inserted), I'd rather have it idle wait until another thread needs to synchronize. Is that possible?

CheckSynchronize has a parameter "timeout" with the default value 0: http://www.freepascal.org/docs-html/rtl/classes/checksynchronize.html

You can pass a different value to wait for a longer period of time (specify the number of milliseconds). There is no equivalent of "wait forever" though.

Jonas

Thanks a lot! Setting it sufficiently high gives me exactly what I need.

One suggestion for the docs: I actually had (admittedly very quickly) tried CheckSynchronize with a timeout before. However, the procedure outclevered me, since for the test I didn't create any threads before going into a loop with CheckSynchronize(2147483647). It just didn't seem to work. , I have now found out that it has sanity checks which make it ignore the timeout when there are no threads created. Shouldn't this be mentioned in the docs?

Thanks again
Roland

Hello,

I think that what you did is the only right solution. Synchronizing threads is tricky, and the default mechanism is meant for GUI apps where the main thread is the GUI thread.

Michael.

I wish there was a way for a thread to asynchronously notify the main thread there is a Synchronize() pending. On Linux I can insert an fd() for a pipe into the gtk event loop and poke data into the pipe from the thread. It's incredibly efficient and saves all the waiting and polling. I've not worked out how to do this on OSX or Win32 yet though.

Brad

If you use the timeout parameter from CheckSynchronize, you do get that effect (if you pass high(longint) as timeout, then you only "poll" if nothing happened for 2^31 miliseconds, which is about 24 days).

Jonas

Err. yeah, but doesn't checksynchronize block until either an event or the timeout?

I'd have thought that would destroy your GUI interactivity.

Brad