SMP, DEVICE_POLLING and fxp LOR

Ed Maste emaste at phaedrus.sandvine.ca
Mon May 30 06:44:46 PDT 2005


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) @ /d2/emaste/cvs_head/src/sys/kern/kern_poll.c:332
 2nd 0xa23e22a0 fxp0 (network driver) @ /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.

--
Ed Maste, Sandvine Incorporated


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