[M3devel] A win32 thread test case

[Jay K]

I fixed the new_slots problem.

I agree there are problems here.  I think Java got away with a similar implementation  because their interface is a bit different.  i.e. the lock and condition are merged, and/or notification  requires the caller to take the lock. We can't do this.  We allow signal/broadcast w/o holding a lock.  We'd have to resort to a global lock I guess.

  I suspect nobody else uses this solution.

I believe we can solve it better and worse than others.

Most libraries do not have their own "CreateThread" function.That is, most libraries let you call pthread_create or Win32 CreateThread,and the library will interoperate with any thread that comes its way.And most libraries don't seem to use thread locals in their solution.By "most libraries", I mean the pthreads on win32 package and Boost.

Modula-3 isn't clearly this way. This isn't great, but it is the currentsituation. I believe it is fixable.That is, Modula-3 I believe requires using its library to create threads.This is not great for interoperation. You want to be able to be usedby code that isn't away of you, that just creates threads in the "normal" wayfor their platform.

And then, either the current state, or a fix I have in mind, can be takenadvantage of to do "directed notify" w/o creating a kernel eventper wait or notify, like other solutions do.

As to the fix, to not require threads go through our "CreateThread",I believe on Windows (which is all that is relevant here), we should havea DllMain that allocates thread locals.

We can only easily have a DllMain if we are a .dll.Or we can use __declspec(thread).__declspec(thread) works if the .exe is statically linked to the exe or the dll,or on Vista and newer, but not in a .dll loaded by LoadLibrary prior to Vista.Perhaps that is good enough.

If we require Vista then we can just drop a bunch of our code and usethe Win32 condition variables presumably.I remain curious how the condition variables work there, i.e. we can'timplement them ourselves, but it is possible they either require kernelsupport or are well beyond our abilities.


 - Jay



> Date: Thu, 28 Jul 2016 15:00:45 -0500
> From: rodney_bates at lcwb.coop
> To: m3devel at elegosoft.com; jay.krell at cornell.edu
> Subject: A win32 thread test case
> 
> I have attached a test case program designed to expose one of the bugs
> I think I see in ThreadWin32.m3.  It runs correctly on AMD64_LINUX.
> I expect it to fail on Windows, but don't have a Windows machine I
> can try it on.
> 
> Anybody willing to try it?  It's a self-contained Main module.  Just
> compile and run it.  It will announce what it finds.
> 
> 
> -- 
> Rodney Bates
> rodney.m.bates at acm.org
 		 	   		  
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