Re: reference counting.. continued..

From: Julian Elischer (julian_at_elischer.org)
Date: 06/13/04

  • Next message: Scott Long: "Re: RFC: API change for sema_timedwait" 
    Date: Sat, 12 Jun 2004 17:59:23 -0700 (PDT)
To: Robert Watson <rwatson@freebsd.org>

    On Sat, 12 Jun 2004, Robert Watson wrote:

    >
    > On Wed, 9 Jun 2004, Poul-Henning Kamp wrote:
    >
    > > I am not in favour of a dedicated API for refcounts.
    > >
    > > A dedicated API works if the refcount is a detached property of the
    > > object, and that is not normally the case outside OO+GC implementations.
    > >
    > > Our reference counts will almost invariably be integral properties of
    > > our objects and therefore has to interact with the remaining object
    > > locking.
    >
    > I don't have a strong feeling about the general need for a refcount API,
    > but I can confirm that many of the interesting objects in the kernel
    > wouldn't lend themselves to such an API. There are many cases where we'll
    > want to protect the reference count using an existing lock, in which case
    > locking built into the reference count API becomes a liability. Socket
    > reference counting is one example of this: in some ways, it's a general
    > purpose reference count, but the GC behavior is specific to sockets and
    > depends on additional uncounted references from file descriptors and the
    > prototocol layer.

    That's the problem... "uncounted references". Either you are counting
    references or you are not..

    >
    > That said, I think making sure people get reference counts right is
    > important: at the very least, I think it would be useful to have a
    > refcount(9) man page with a well thought out example of a simple reference
    > count implementation, or a pointer at such an implementation (ucred isn't
    > bad).
    >
    > Robert N M Watson FreeBSD Core Team, TrustedBSD Projects
    > robert@fledge.watson.org Senior Research Scientist, McAfee Research
    >
    >
    >

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  • Next message: Scott Long: "Re: RFC: API change for sema_timedwait"

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