Re: SMP, DEVICE_POLLING and fxp LOR

On Mon, May 30, 2005 at 09:44:43AM -0400, Ed Maste wrote:
> A few days ago I posted to -stable about a LOR observed on our 5.4-based
> tree with SMP, DEVICE_POLLING and fxp:
> http://lists.freebsd.org/pipermail/freebsd-stable/2005-May/015376.html
> Contrary to my earlier assertion, em does not have a problem.
> 
> We do have a fair amount of local diffs, so I've now confirmed this is easily
> reproduced on unmodified -CURRENT as of 05/28.
> 
> My config file has
> options         SMP
> options         DEVICE_POLLING
> device          fxp
> (full config file at http://www.maste.org/~ed/sv/STOCK.1 )
> 
> lock order reversal
>  1st 0xa0783860 Giant (Giant) _at_ /d2/emaste/cvs_head/src/sys/kern/kern_poll.c:332
>  2nd 0xa23e22a0 fxp0 (network driver) _at_ /d2/emaste/cvs_head/src/sys/dev/fxp/if_fxp.c:1473
> KDB: stack backtrace:
> kdb_backtrace(0,ffffffff,a07a6168,a07a4750,a0759160) at 0xa0585789 = kdb_backtrace+0x29
> witness_checkorder(a23e22a0,9,a070a173,5c1) at 0xa058f74c = witness_checkorder+0x55c
> _mtx_lock_flags(a23e22a0,0,a070a173,5c1) at 0xa05652f8 = _mtx_lock_flags+0x60
> fxp_poll(a23e2000,1,5) at 0xa04fa001 = fxp_poll+0x29
> netisr_poll(0) at 0xa0567070 = netisr_poll+0x188
> swi_net(0) at 0xa05d9041 = swi_net+0x81
> ithread_loop(a2309000,c5d8fd38,a2309000,a055aba8,0) at 0xa055acc8 = ithread_loop+0x120
> fork_exit(a055aba8,a2309000,c5d8fd38) at 0xa055a0f0 = fork_exit+0xa0
> fork_trampoline() at 0xa06ad31c = fork_trampoline+0x8
> 
> The ether_poll_deregister in fxp_stop() looks to be the culprit.
> 
This LOR is well-known and will go away as soon as we commit our WIP
changes for polling(4).  I have no firm plans when it happens though.


Cheers,
-- 
Ruslan Ermilov
ru_at_FreeBSD.org
FreeBSD committer