Re: call for bge(4) testers

On Thu, Aug 24, 2006 at 04:43:54AM +0400, Oleg Bulyzhin wrote:
 > 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?
 > 

I can't remember what caused this. Need more coffee. :-(
If my memory serve me right it's related with ioctls.
I guess you can easily experiment with removing MTX_RECURSE flag
in the driver.

-- 
Regards,
Pyun YongHyeon