Re: call for bge(4) testers

On Thu, Aug 24, 2006 at 09:30:35AM +0900, Pyun YongHyeon wrote:
> On Wed, Aug 23, 2006 at 04:54:34PM +0400, Oleg Bulyzhin wrote:
>  > On Wed, Aug 23, 2006 at 04:40:35PM +0400, Oleg Bulyzhin wrote:
>  > > On Wed, Aug 23, 2006 at 09:55:54AM +0900, Pyun YongHyeon wrote:
>  > > > On Wed, Aug 23, 2006 at 12:43:42AM +0400, Oleg Bulyzhin wrote:
>  > > >  > On Tue, Aug 22, 2006 at 02:44:34PM +0200, Michael Reifenberger wrote:
>  > > >  > > On Tue, 22 Aug 2006, Pyun YongHyeon wrote:
>  > > >  > > ...
>  > > >  > > >I'm not familiar with vge(4) and don't have hardwares supported by
>  > > >  > > >vge(4). Because vge(4) supports a kind of interrupt moderation, there
>  > > >  > > >is a possiblity to have the same issue seen on em(4).
>  > > >  > > >If you want my blind patch I can send a patch for you.
>  > > >  > > >
>  > > >  > > Yes, please!
>  > > >  > > I can test it (on RELENG_6 though).
>  > > >  > 
>  > > >  > I have an idea why those timeouts can happen. Could you please test
>  > > >  > attached patch? It may help (or may not). Anyway would be fine
>  > > >  > to know results.
>  > > >  > 
>  > > > 
>  > > > Since vge(4) uses MTX_RECURSE mutex and miibus(4) handler is
>  > > > protected with the mutex I guess it wouldn't help much.
>  > > > I guess it needs a seperate mutex to protect miibus(4) handler
>  > > > and should remove the use of MTX_RECURSE.
>  > > 
>  > > Hmm.
>  > > 1) _ifmedia_upd() & _ifmedia_sts() functions are not called from mii layer.
>  > > 2) As i can see MII layer is not protected by anything, unless you
>  > > specially acquire driver lock prior to calling mii_ function.
>  > > Locking ifmedia callbacks should be done (though, it may not help
>  > > with watchdogs timeout), otherwise we have race on accessing PHY registers.
>  > > (kern/98738).
>  > > 
>  > > As i can see, random watchdog timeouts was reported for em, bge, vge, sk
>  > > (and maybe others, those ones which i remember) drivers.
>  > > All of them has unlocked _ifmedia_ functions.
>  > > 
>  > > My idea was: perhaps, under certain condition, concurrent access to PHY could
>  > > lead to hardware deadlock.
>  > > 
>  > > 
>  > > > vge(4) also has a bug
>  > > > if mbuf chain is too long(7 or higher) and defragmentation with
>  > > > m_defrag(9) fails it would access an invalid mbuf chain.
>  > > > All these requires lots of work and need a real hardware.
>  > > > Oleg, if you have hardware, would you fix it?
>  > > 
>  > > Unfortunately i don't have vge hardware.
>  > > > 
>  > > > -- 
>  > > > Regards,
>  > > > Pyun YongHyeon
>  > > 
>  > > -- 
>  > > Oleg.
>  > > 
>  > 
>  > Forgot one thing: i think we need no dedicated mutex for mii layer if we lock
>  > ifmedia callbacks.
>  > 
> 
> If we use the diver mutex in MII access it would require MTX_RECURSE
> mutex. I want simple MTX_DEF mutex.

Could you please explain why MTX_RECURSE is required?

> 
> -- 
> Regards,
> Pyun YongHyeon

-- 
Oleg.