Date: Mon, 16 Oct 1995 13:01:07 -0700 (MST) From: Terry Lambert <terry@lambert.org> To: matt@lkg.dec.com (Matt Thomas) Cc: julian@freefall.freebsd.org, hackers@freefall.freebsd.org Subject: Re: suggested changes to mbuf routines Message-ID: <199510162001.NAA25213@phaeton.artisoft.com> In-Reply-To: <199510151123.LAA01923@whydos.lkg.dec.com> from "Matt Thomas" at Oct 15, 95 11:21:25 am
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>
>
> In <199510141119.EAA05158@freefall.freebsd.org> , you wrote:
>
> I find the method of doing the references as done in Digital UNIX
> (aka DEC OSF/1) quite clean. Basically the m_ext struct gets an
> queue entry added. When the extended mbuf is first allocated, the
> link queue entry merely points to itself (an empty queue). As more
> references are made, their queues get linked together. As references
> are removed, their queues get unlinked.
>
> To see if there is a non-zero reference count, imply see if the queue
> entry points to itself.
>
>
> /* description of external storage mapped into mbuf, valid if M_EXT set */
> struct m_ext {
> caddr_t ext_buf; /* start of buffer */
> #if __STDC__
> void (*ext_free)(caddr_t, u_long, caddr_t);
> #else
> void (*ext_free)(); /* free routine if not the usual */
> #endif
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> u_int ext_size; /* size of buffer, for ext_free */
> caddr_t ext_arg; /* additional ext_free argument */
> struct ext_refq { /* reference list */
> struct ext_refq *forw, *back;
> } ext_ref;
> };
>
> #define MCLREFERENCED(m) \
> ((m)->m_ext.ext_ref.forw != &((m)->m_ext.ext_ref))
This, I like.
This:
> void (*ext_free)(caddr_t, u_long, caddr_t);
Should be:
> void (*ext_free) __P((caddr_t, u_long, caddr_t));
Terry Lambert
terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.
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