Date: Sat, 5 Dec 2009 21:40:03 GMT From: Benjamin Kaduk <kaduk@MIT.EDU> To: freebsd-net@FreeBSD.org Subject: Re: kern/140036: [iwn] [lor] lock order reversal with iwn0_com_lock and iwn0 softc lock Message-ID: <200912052140.nB5Le3FR048933@freefall.freebsd.org>
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The following reply was made to PR kern/140036; it has been noted by GNATS.
From: Benjamin Kaduk <kaduk@MIT.EDU>
To: Bernhard Schmidt <bschmidt@techwires.net>
Cc: bug-followup@freebsd.org
Subject: Re: kern/140036: [iwn] [lor] lock order reversal with iwn0_com_lock
and iwn0 softc lock
Date: Sat, 5 Dec 2009 16:30:35 -0500 (EST)
On Sat, 5 Dec 2009, Benjamin Kaduk wrote:
>
> I'll update and revert my change to net80211/ieee80211_proto.c and
> see what changes.
Okay, now I only get a LOR on beacon miss (no panic):
lock order reversal:
1st 0xffffff8000309010 iwn0 (network driver) @ /usr/devel/iwn/freebsd/sys/modules/iwn/../../dev/iwn/if_iwn.c:2655
2nd 0xffffff800033d018 iwn0_com_lock (iwn0_com_lock) @ /usr/src/sys/net80211/ieee80211_proto.c:1365
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2a
_witness_debugger() at _witness_debugger+0x2e
witness_checkorder() at witness_checkorder+0x81e
_mtx_lock_flags() at _mtx_lock_flags+0x78
ieee80211_beacon_miss() at ieee80211_beacon_miss+0x2e
iwn_notif_intr() at iwn_notif_intr+0x33a
iwn_intr() at iwn_intr+0x334
intr_event_execute_handlers() at intr_event_execute_handlers+0x66
ithread_loop() at ithread_loop+0xb2
fork_exit() at fork_exit+0x12a
fork_trampoline() at fork_trampoline+0xe
--- trap 0, rip = 0, rsp = 0xffffff803a97ed30, rbp = 0 ---
I kind of expect that it's a bad idea to drop the softc lock around
the call to ieee80211_beacom_miss() from iwn_notif_intr(), but
don't see an easy alternative.
More concerning, though, is the firmware error that was logged
some twenty seconds after the beacon miss, leaving networking
in an unuseable state:
firmware error log:
error type = "SYSASSERT" (0x00000005)
program counter = 0x00001E28
source line = 0x00000696
error data = 0x0000000100000696
branch link = 0x000008FA000008FA
interrupt link = 0x000008B200000000
time = 2190683577
driver status:
tx ring 0: qid=0 cur=99 queued=0
tx ring 1: qid=1 cur=0 queued=0
tx ring 2: qid=2 cur=0 queued=0
tx ring 3: qid=3 cur=7 queued=0
tx ring 4: qid=4 cur=186 queued=0
tx ring 5: qid=5 cur=0 queued=0
tx ring 6: qid=6 cur=0 queued=0
tx ring 7: qid=7 cur=0 queued=0
tx ring 8: qid=8 cur=0 queued=0
tx ring 9: qid=9 cur=0 queued=0
tx ring 10: qid=10 cur=0 queued=0
tx ring 11: qid=11 cur=0 queued=0
tx ring 12: qid=12 cur=0 queued=0
tx ring 13: qid=13 cur=0 queued=0
tx ring 14: qid=14 cur=0 queued=0
tx ring 15: qid=15 cur=0 queued=0
tx ring 16: qid=16 cur=0 queued=0
tx ring 17: qid=17 cur=0 queued=0
tx ring 18: qid=18 cur=0 queued=0
tx ring 19: qid=19 cur=0 queued=0
rx ring: cur=26
Hm, maybe I should move this to not-this-ticket ...
-Ben
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