Re: [PATCH] opensm/osm_state_mgr.c: force heavy sweep when fabric consists of single switch

[Sasha Khapyorsky <sashak-smomgflXvOZWk0Htik3J/w@public.gmane.org>]

On 10:24 Fri 13 Nov     , Eli Dorfman wrote:
> On Thu, Nov 12, 2009 at 2:50 PM, Yevgeny Kliteynik
> <kliteyn-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org> wrote:
> > Eli Dorfman (Voltaire) wrote:
> >>
> >> Yevgeny Kliteynik wrote:
> >>>
> >>> Eli Dorfman (Voltaire) wrote:
> >>>>
> >>>> Yevgeny Kliteynik wrote:
> >>>>>
> >>>>> Eli Dorfman (Voltaire) wrote:
> >>>>>>
> >>>>>> Yevgeny Kliteynik wrote:
> >>>>>>>
> >>>>>>> Eli Dorfman (Voltaire) wrote:
> >>>>>>>>
> >>>>>>>> Yevgeny Kliteynik wrote:
> >>>>>>>>>
> >>>>>>>>> Yevgeny Kliteynik wrote:
> >>>>>>>>>>
> >>>>>>>>>> Line Holen wrote:
> >>>>>>>>>>>
> >>>>>>>>>>> On 11/ 4/09 04:54 PM, Yevgeny Kliteynik wrote:
> >>>>>>>>>>>>
> >>>>>>>>>>>> Line Holen wrote:
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> On 11/ 4/09 10:47 AM, Yevgeny Kliteynik wrote:
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> Sasha Khapyorsky wrote:
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> On 12:26 Tue 03 Nov     , Yevgeny Kliteynik wrote:

This is a nice and productive discussion. But please remove a context
which is not related to the current point - it helps to follow thread.

[snip]

> >> The PSC bit should be cleared before SM reads the PortInfo from that
> >> switch.
> >
> > This may be true, but do you really want to require
> > Set(SwitchInfo) *completion* before getting other PortInfo
> > MADs from this switch?
> 
> I don't see any other good alternative and I'm sure this will solve
> all race conditions.

I agree with Eli - if we want to prevent PSC bit loss (which can be
relevant for any subnet/SM topology), we need to clear it first and than
to fetch PortInfo. Obviously this may have some performance penalty, but
proper discovery is more important.

> I suggest that when PSC bit is set in SwitchInfo response we will send
> Set(SwitchInfo) to clear the PSC bit and
> in SwitchInfo response send Get(PortInfo) - this requires adding
> another flag to the mad context.

Another flag or reusing one of existing flag.

> If PSC bit is not set or SM is not in Master state Get(PortInfo) will
> be done in the immediately.
> 
> what do you think?

Another potential issue is to avoid a secondary trap triggered sweep for
cases when PSC change is already cached.

Basically looks like a right direction for me.

Sasha
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