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Date:      Wed, 9 Sep 2009 13:51:17 -0500
From:      Brandon Gooch <jamesbrandongooch@gmail.com>
To:        Jung-uk Kim <jkim@freebsd.org>
Cc:        bzeeb+freebsd+lor@zabbadoz.net, Felix Stolba <alleepsilonkleinereins@gmail.com>, freebsd-current@freebsd.org
Subject:   Re: LOR acpi_ibm module
Message-ID:  <179b97fb0909091151g502c846fq5070f84381f9efa5@mail.gmail.com>
In-Reply-To: <200909091425.15003.jkim@FreeBSD.org>
References:  <179b97fb0905301355n2a422e05j665fc3a551ce06f1@mail.gmail.com> <4AA7EAB2.5040403@googlemail.com> <200909091425.15003.jkim@FreeBSD.org>

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On Wed, Sep 9, 2009 at 1:25 PM, Jung-uk Kim<jkim@freebsd.org> wrote:
> On Wednesday 09 September 2009 01:49 pm, Felix Stolba wrote:
>> Brandon Gooch schrieb:
>> > lock order reversal:
>> > =A01st 0xffffffff807cf200 sysctl lock (sysctl lock) @
>> > /usr/src/sys/kern/kern_sysctl.c:1608
>> > =A02nd 0xffffffff80bf1de0 ACPI IBM extras (ACPI IBM extras) @
>> > /usr/src/sys/modules/acpi/acpi_ibm/../../../dev/acpi_support/acpi
>> >_ibm.c:481 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
>> > _sx_xlock() at _sx_xlock+0x54
>> > acpi_ibm_sysctl() at acpi_ibm_sysctl+0x4f
>> > sysctl_root() at sysctl_root+0xe3
>> > userland_sysctl() at userland_sysctl+0x158
>> > __sysctl() at __sysctl+0xaa
>> > syscall() at syscall+0x1dd
>> > Xfast_syscall() at Xfast_syscall+0xd0
>> > --- syscall (202, FreeBSD ELF64, __sysctl), rip =3D 0x80073769c,
>> > rsp =3D 0x7fffffffda58, rbp =3D 0x4 ---
>>
>> I'm getting the same LOR at boot in 9.0-current (source from 7th of
>> september).
>
> It is generally harmless but really annoying.
>
> Jung-uk Kim
>

I haven't been running a kernel with WITNESS (or any debugging) for a
couple of weeks, so I forgot about it.

Originally, I wondered if this locking problem(?) was causing a
strange issue when I invoked a script via devd (a call to a script to
handle ACPI events through acpi_ibm.ko), in this case, an ACPI screen
brightness function: Occasionally, the screen brightness would not
adjust when I used the Fn keys, only to eventually, "pop" all of the
requests I sent off of the devd command table, usually with a long
delay.

If I started devd in foreground mode and watched the command output in
the terminal, commands were "pushed" and "popped" immediately; all was
well.

I was never able to put it all together, and it was only a minor
annoyance, after all.

-Brandon



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