Re: A Quick Question about Threads

From: Jason Winnebeck (yg-boost-users_at_[hidden])
Date: 2003-07-31 17:05:49

Mark Sizer wrote:
> After much debate, we adopted the following coding standard:
> 
> { boost::mutex::scoped_lock lock(_mtxShared);
> 
>    // do whatever
> 
> }

That standard is great.  RAII is great and I love it.  I'm not using 
boost threads, but I would have had I known about them at the time.  I 
have working code so I'm not going to change it.

I use exceptions in my program as well, so I use something that works 
(from that example) identical to the scoped_lock.  I usually do 
something like:

void Object::function() {
   LockMutex lock( mtx );
   //whatever
}

Then it is exception and "return" safe.  I have thought about using the 
style you give all of the time, but I only do it now if I must (because 
I want the mutex to lock early).  The drawback is that you can't do 
something like this with the RAII methods.

mtx.lock();
mtx2.lock();
mtx.release();
mtx2.release();

But I've never seen a case so far where I'm required to do that.  I do 
have a LockMutexEx object that allows you to call release to release 
early.  I make sure to use it as rarely as possible, but I've used it I 
believe once on a condition variable where I wanted to keep it locked if 
my condition was met.  I doesn't sound like I'd need it when describing 
it here but I did use it once.  I can see a problem with it since with 
RAII, you are supposed to "have the resource" while the object exists.

Jason