Subj : Re: reliability of setting thread priority
To   : comp.programming.threads
From : gottlobfrege
Date : Fri Feb 25 2005 06:00 am


Alexander Terekhov wrote:
> gottlobfrege@gmail.com wrote:
>
> [... DCSI and named mutexes ...]
>
> > I had a real life case where there was possibly going to be 100s of
> > these objects used, so speed matters.
>
> Yeah, it would kinda matter if you have 100s of threads and 100s of
> locals static all stuck in the initialization phase. Hardly "real
> life case".
>
> regards,
> alexander.

No 100s of threads was not a concern, just hundreds of objects.  In my
original version, I was calling CreateMutex (with a unique name based
on process ID and object address, etc) for *each* object - ie there was
no contention between 2 different objects being initted, just if the
same object was being initted.  So I wanted to avoid that many
CreateMutexes.

I also considered _one_ mutex for all objects (per process), but then

- the class has a static handle, and needs to be defined in *some* cpp.
 Not a real problem, but it was otherwise a h file only solution -
easier to use/share. (I could use __declspec(selectany) but that would
obviously need per-compiler porting.)
And I have to carefully set the handle:
   if (!globalhandle) // or atomic read to ensure memory barrier
   {
       tmphandle = CreateMutex(somePerProcessName);
       oldhandle = exchange(&globalhandle, tmphandle);
       if (oldhandle)
          CloseHandle(oldhandle); // don't miscount
   }
- I could not bother saving the handle and let CreateMutex find it for
me by name, but then I would never get around to deleting it at program
close.  Windows will do it for me anyhow, but I'm not sure about other
platforms.

So even with a mutex I still need lots of 'exchange logic', so in that
respect it doesn't seem better or worse than what I have.

But it may very well be better in other respects.  That's why I'm here
asking.  Part of the bigger picture is that I think I understand most
of the pros and cons of the other methods, but was unsure of the
messing with thread priorities.

At the end of the day, I might go back to using a mutex, but was
exploring other possibilities.

Tony.

.