WaitAll limitation
I heard there is limitation when using waitall on multiple threads 开发者_如何学编程(# of threads to wait?). Can anyone give details?
I think the restriction you are referring to is not on the number of threads; it is on the number of handles being waited on. From the MSDN page for WaitHandle.WaitAll(WaitHandle[])
:
On some implementations, if more than 64 handles are passed, a NotSupportedException is thrown.
On the rare occasion that this issue has cropped, I have normally worked around it with:
WaitHandle[] handles = ...
foreach(var waitHandle in handles)
waitHandle.WaitOne();
For completeness, the other restrictions appear to be:
If the array contains duplicates, the call fails with a DuplicateWaitObjectException.
The WaitAll method is not supported on threads that have STAThreadAttribute.
Are you thinking of the STA (single-threaded apartment) limitation of a winform app?
If so, I handle this by simply checking if the 'work queue' is empty after each thread has done it's processing, and calling .WaitOne() on a single ManualResetEvent object that the main thread owns instead of using .WaitAll() at all.
Like this:
moSolverEvent = new ManualResetEvent(false);
ProcessResult(new SolverWorkInProgress());
//Wait here until the last background thread reports in
moSolverEvent.WaitOne();
And then the worker threads are doing this:
if (mhSolverWorkQueue.Count == 0) moSolverEvent.Set();
It works spectacularly well, and avoids any issues with WaitAll(), even in a WinForms app. After all, you're not really waiting for the threads to be done... you're waiting for the WORK to be done. :-)
Just be sure to do the appropriate locking on each of these objects so your threads don't step all over each other.
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