Re: [PATCH V1 FIX for-3.19] IB/ipoib: Fix broken multicast flow

[Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

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On Fri, 2015-01-09 at 10:32 +0200, Or Gerlitz wrote:
> On Wed, Jan 7, 2015 at 5:04 PM, Or Gerlitz <ogerlitz-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org> wrote:
> > From: Erez Shitrit <erezsh-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
> >
> > Following commit 016d9fb25cd9 "IPoIB: fix MCAST_FLAG_BUSY usage"
> > both IPv6 traffic and for the most cases all IPv4 multicast traffic
> > aren't working.
> 
> Doug, can you ack the breakage introduced by your commit and the fix?

I haven't double checked the breakage, I'll take your word for it (at
the time I did my work, I had multicast debugging on and I verified the
join/leave process, but I had assumed that the process would work the
same for optional multicast groups as it does for the IPoIB broadcast
group and other default IPoIB groups, so I didn't specifically test
additional multicast groups above and beyond the broadcast/etc groups).

However, the fix is not workable.  In particular, as soon as this patch
is added to the kernel, you will start getting messages like this:

mlx4_ib0: ipoib_mcast_leave on an in-flight join

Every time you get this message, you've run into a "shouldn't ever
happen" situation.  If this happens, then we've lost track of the mcast
flags settings or we've genuinely tried to remove a mcast group where
the lower layer is still working on our join.  Either way, it means
we've screwed up.  Further, with this patch in place, I'm seeing random
acts of badness now with non-default IPoIB pkey joins.  Sometimes they
work, sometimes they don't.

So, no, this patch doesn't work.  I'll do some more investigating and
report back.

> Or.
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-- 
Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
              GPG KeyID: 0E572FDD



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