Andreas Henriksson wrote:
> On Fri, Mar 26, 2004 at 12:14:57PM +0200, Denis Vlasenko wrote:
> 
> <snip>
> 
>>BTW, my box is indeed slow and low on RAM, this fits.
>>
> 
> 
> I have only been looking at problems with races between the interrupt
> handler and the rest of the driver code.. there might be a bunch of
> problems with failed memory allocations that hasn't bitten me.
> 
> 
>>Regarding your patch: I looked in start_tx(). Apart from latent
>>bug in commented out part of code:
>>	next = (struct fealnx *) np->cur_tx_copy.next_desc_logical;
>>which must be
>>	next = (struct fealnx_desc *) np->cur_tx_copy->next_desc_logical;
>>I can't see anything racy there. The function just submits more
>>tx buffers for the card, it never touch cur_tx or cur_tx->skbuff...
> 
> 
> Francois Romieu explains the race in a comment to the bug I opened in
> the bugzilla.
> 
> http://bugzilla.kernel.org/show_bug.cgi?id=1902#c1
> 
> The problem is that really_tx_count and similar parts of the private
> structure isn't atomically updated and both the interrupt handler and
> the start_tx function updates them.
> (they are regular integers instead of atomic_t)
> 
> 
>>If I miss something and it indeed races with interrupt, you
>>definitely need to add
>>        spin_lock(&np->lock);
>>...
>>        spin_unlock(&np->lock);
>>around interrupt handler body or at least around tx part
>>of it, or else your patch is incomplete (race will still
>>be possible on SMP).
>>
> 
> 
> I came to the conclusion that there should be a spinlock in the
> interrupt handler yesterday, but it won't effect me at all since I don't
> have SMP (nor preempt) so I'll leave it for now anyway.
> 
> 
>>Anyway, I applied your patch and flooded with UDP again.
>>My box did not oops. Unfortunately, it did not oops when
>>I reverted back to old, presumably buggy driver. I cannot
>>reproduce it anymore with old driver too! Bad. :(
> 
> 
> I haven't been able to reproduce a kernel panic with my patch eighter.
> And I've been transfering Terabytes of traffic during the last weeks (or
> maybee it's months, well anyway.. I've done enough testing to say that
> the card works "good enough" in this machine atleast).
> And I've even tried your udp test..
> 
> Although I now have the myson/fealnx card in my p3-900 (256Mb)
> workstation instead of the old p-166 (40Mb) which served as a gateway before.
> It might just be that it's harder to trigger on newer/bigger machines.
> Maybee I should power up my p-166 again.. I actually have 2 of these
> cards so I can have one in each machine.. :)

Well really, somebody needs to port Donald Becker's myson driver to 2.6 
APIs...  I would like to get rid of fealnx, or somebody needs to spend a 
decent amount of time fixing it.

Does the attached patch fix the issue?

	Jeff