Subj : Re: Lockable objects
To   : comp.programming.threads
From : Uenal Mutlu
Date : Sat May 21 2005 03:31 pm

"Peter Dimov" wrote
> Uenal Mutlu wrote:
>
> > You said it: diagnostics, and debug.
> > Esp. in such situations like below:
> >
> > void f()
> > { // requires that object must be locked before calling this func
> >
> >  assert(!m.IsLocked());
> >
> >  //...
> > }
>
> This makes sense as long as IsLocked() only returns true if the current
> thread is the one holding the lock. This in effect requires an owner field.

True, actually IsLocked() returns true if both is true.
A better method would be to have:
  bool IsLocked();     // return true if mutex locked by anybody
  bool IsLockedByMe();   // return true if locked and the current thread is the lock owner

void f()
{ // requires that object must be locked before calling this func
 assert(!m.IsLockedByMe());
 //...
}

> Another approach that works on application level is to enforce the use of
> lock classes (such as boost::scoped_lock) and pass such a lock to f.
>
> void f( scoped_lock & lock )
> {
>     assert( lock.locked() );
>     assert( lock.mutex() == &m );
>
>     // ...
> }

Yep.

.