Re: [boost] storing intrusive_ptr in atomic?!

Subject: Re: [boost] storing intrusive_ptr in atomic?!
From: Oliver Kowalke (oliver.kowalke_at_[hidden])
Date: 2013-10-25 07:43:38

2013/10/25 Giovanni Piero Deretta <gpderetta_at_[hidden]>

> that's the tricky part. To adjust the reference count, you must load and
> dereference the pointer itself, but between those two operations another
> thread might come in, replace the pointer, adjust the original pointer
> count down and free the pointed object, together with the counter. You need
> some way to defer destruction till a safe point (RCU, hazard pointers,
> etc).
>

what about this

// use-counter in T is an atomic too
array< atomic< intrusive_ptr< T > >, 100 > a;

intrusive_ptr< T > p(...);
intrusive_ptr_add_ref( p.get() );
// add an intrusive_ptr to the array
if ( a[index].compare_exchange_strong(null_ptr,p) ) {
  // successful added
}

// remove an interusive_ptr from array
intrusive_ptr< T > e; // points to nothing
if ( ! a[index].compare_exchange_strong(e, null_ptr) ) {
  // successfull removed
  intrusive_ptr_release( e.get() );
}