Re: TG3 data corruption (TSO ?)

[Segher Boessenkool <segher@kernel.crashing.org>]

> > I've been chasing with Segher a data corruption problem lately.
> > Basically transferring huge amount of data (several Gb) and I get
> > corrupted data at the rx side. I cannot tell for sure wether what  
> > I've
> > been observing here is the same problem that segher's been seing  
> > on is
> > blades, he will confirm or not. He also seemed to imply that  
> > reverting
> > to an older kernel on the -receiver- side fixed it, which makes me
> > wonder, since it's looks really like a sending side problem (see
> > explanation below), if some change in, for exmaple, window scaling,
> > might hide or trigger it.
>
> Please send me lspci and tg3 probing output so that I know what
> tg3 hardware you're using.

I use a 5780 rev. A3, but the problem is not limited to this chip.

> I also want to look at the tcpdump or
> ethereal on the mirrored port that shows the packet being corrupted.

I don't have such, sorry.

> > That's all the data I have at this point. I can't guarantee 100% that
> > it's a TSO bug (it might be a bug that TSO renders visible
> > due to timing
> > effects) but it looks like it since I've not reproduced yet with TSO
> > disabled.

It seems to indeed to only be exposed by TSO, not actually a
bug of it /an sich/.

I've got a patch that seems so solve the problem, it needs more testing
though (maybe Ben can do this :-) ).  The problem is that there should
be quite a few wmb()'s in the code that are just not there; adding some
to tg3_set_txd() seems to fix the immediate problem but more is needed
(and I don't see why those should be needed, unless tg3_set_txd() is
updating a life ring entry in place or something like that).

More testing is needed, but the problem is definitely the lack of memory
ordering.


Segher

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