Date: Sun, 25 Dec 2011 12:45:55 +0300 From: Sergey Kandaurov <pluknet@gmail.com> To: John Baldwin <jhb@freebsd.org> Cc: Bjoern Zeeb <bz@freebsd.org>, net@freebsd.org Subject: Re: [PATCH] Minor fixes to netinet6/icmp6.c Message-ID: <CAE-mSOJ722UNqkVNs%2B8_LQ4pVt4VTmSkDhr3re5aDhsHPfQffQ@mail.gmail.com> In-Reply-To: <4EF6752C.4040109@FreeBSD.org> References: <201112231446.38057.jhb@freebsd.org> <CAE-mSOLryQb6n0RcxM=LHFCLN=25Tfk5bLnLjK1e5XbU5ncmWw@mail.gmail.com> <4EF6752C.4040109@FreeBSD.org>
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On 25 December 2011 04:58, John Baldwin <jhb@freebsd.org> wrote:
> On 12/23/11 6:38 PM, Sergey Kandaurov wrote:
>>
>> On 23 December 2011 23:46, John Baldwin<jhb@freebsd.org> wrote:
>>>
>>> I found these nits while working on the patches to convert if_addr_mtx to
>>> an
>>> rwlock. The first change is cosmetic, it just un-inlines a
>>> TAILQ_FOREACH().
>>> The second change is an actual bug. The code is currently reading
>>> TAILQ_FIRST(&V_ifnet) without holding the appropriate lock.
>>>
>>> Index: icmp6.c
>>> ===================================================================
>>> --- icmp6.c (revision 228777)
>>> +++ icmp6.c (working copy)
>>> @@ -1780,7 +1780,7 @@ ni6_addrs(struct icmp6_nodeinfo *ni6, struct mbuf
>>> }
>>>
>>> IFNET_RLOCK_NOSLEEP();
>>> - for (ifp = TAILQ_FIRST(&V_ifnet); ifp; ifp = TAILQ_NEXT(ifp,
>>> if_list)) {
>>> + TAILQ_FOREACH(ifp,&V_ifnet, if_list) {
>>> addrsofif = 0;
>>> IF_ADDR_LOCK(ifp);
>>> TAILQ_FOREACH(ifa,&ifp->if_addrhead, ifa_link) {
>>
>>
>> FWIW, there are much more of them in netinet6.
>> Some time ago I started to un-expand them to queue(3).
>> [not unfinished yet..]
>
>
> I went ahead and did a sweep for queue(3) changes in netinet6. I went a bit
Great, thank you! This sweep is long overdue.
> further and removed things like the ndpr_next hack, etc. This only includes
> queue(3) changes though, not your other fixes like moving common code out of
Oops, yeah. This is an unrelated change.
> blocks. I also fixed a few places to use *_EMPTY() instead of checking
> *_FIRST() against NULL. There should be no functional change.
>
> http://www.FreeBSD.org/~jhb/patches/inet6_queue.patch
Looks good. Please, commit with two notes:
a) You changed a loop with precondition
while (i < DRLSTSIZ) { ... }
into
if (i >= DRLSTSIZ)
and moved it below i++ increment, which effectively became
a loop with post-condition like do { ...} while ().
To preserve the current behavior I would move this check up
right under *_FOREACH() loop, like this:
TAILQ_FOREACH(dr, &V_nd_defrouter, dr_entry) {
if (i >= DRLSTSIZ)
break;
b)
It should be safe to use non-SAFE() FOREACH() variants of
queue(3) macros for most occurrences. SAFE() versions are
usually only used when you need to add/remove an element
on list w/o need to subsequent restart the *_FOREACH() loop.
--
wbr,
pluknet
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