RFC: small syscons and kbd patch

[Paul B. Mahol]

On 12/4/08, Paul B. Mahol <onemda at gmail.com> wrote:
> On 12/4/08, Maksim Yevmenkin <maksim.yevmenkin at gmail.com> wrote:
>> On Thu, Dec 4, 2008 at 3:24 AM, Garrett Cooper <yanefbsd at gmail.com> wrote:
>>> On Tue, Dec 2, 2008 at 5:01 PM, Maksim Yevmenkin
>>> <maksim.yevmenkin at gmail.com> wrote:
>>>> Dear Hackers,
>>>>
>>>> can someone please review the attached small patch for syscons and
>>>> kbd? it should be a no-op mostly. the patch basically does
>>>>
>>>> 1) removes bogus layering in syscons, i.e. basically removes
>>>> sccngetch();
>>>> 2) implements advisory lock for kbd (based on atomic(9));
>>>> 3) implements new POLLED flag for kbd;
>>>>
>>>> this is a part of a plan to fix keyboard access races in syscons.
>>>>
>>>> thanks,
>>>> max
>>>
>>> Max,
>>>     Why are you double and triple negating on this line?
>>>
>>> +       return (atomic_cmpset_acq_int(&kbd->kb_locked, !!!on, !!on));
>>
>> the idea was to ensure that kbd->kb_locked variable only takes values
>> 0 (zero) and 1 (one).
>>
>> thanks,
>> max
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>
> Maybe it is usefull to report, maybe not.
>
> I'm experiencing keyboard (atkbd) death now and then when inside Xorg once
> Xorg is started in following (racey) way:
>
> alias onlyx             "/usr/local/bin/xinit -- -nolisten tcp -br & &&
> exit"
>
> and /etc/csh.logout:
>
> echo $TERM | grep cons25 >> /dev/null && clear && vidcontrol -C
>
> I will test it and report if it fix my "problem".

No luck.
Typing blindly I managed to panic from kdb, and I got only this:

KDB: enter: manual escape to debugger
panic: from debugger
cpuid = 1
KDB: stack backtrace:
panic: bufwrite: buffer is not busy???
cpuid = 1
KDB: enter: panic
exclusive sleep mutex Giant (Giant) r = 1 (0xc0725a70) locked @ /usr/src/sys/dev
/syscons/syscons.c:618

-- 
Paul