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Message-ID: <44F44CAA.2000203@cisco.com>
Date: Tue, 29 Aug 2006 10:18:18 -0400
From: Randall Stewart <rrs@cisco.com>
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To: John-Mark Gurney <gurney_j@resnet.uoregon.edu>
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Cc: freebsd-net@freebsd.org, andre@freebsd.org
Subject: Re: Problem with uipc_mbuf.c
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John-Mark:
Ok, I confirmed it...
Changing it to be
atomic_fetchadd_int(m->m_ext.ref_cnt, -1) == 1)
Fixes the problem.. no more leaks :-D
R
John-Mark Gurney wrote:
> Randall Stewart wrote this message on Mon, Aug 28, 2006 at 17:04 -0400:
>
>> atomic_fetchadd_int(m->m_ext.ref_cnt, -1) == 0) {
>
> ^
>
> This should be 1 not 0.. as apparently fetchadd_int returns the old value
> (at least that's what atomic(9) says), which means that if we ever race
> on this comparision, we won't free though we should of...
>
> if we look at refcount.h, it does:
> return (atomic_fetchadd_int(count, -1) == 1);
>
> which release a reference and apparently returns true if it needs to
> be free'd...
>
> Though the wierd part is that andre, "fixed" it to be 0 in 1.157:
> Fix a logic error introduced with mandatory mbuf cluster refcounting and
> freeing of mbufs+clusters back to the packet zone.
>
>
>>I am thinking about restoring the old code.. since
>>it appears to work...
>>
>>Any comments or help would be appreciated..
>
>
> Lets see what andre has to say about this.
>
--
Randall Stewart
NSSTG - Cisco Systems Inc.
803-345-0369 <or> 815-342-5222 (cell)