Re: RFC: small syscons and kbd patch

On 12/4/08, Maksim Yevmenkin <maksim.yevmenkin_at_gmail.com> wrote:
> On Thu, Dec 4, 2008 at 8:00 AM, Paul B. Mahol <onemda_at_gmail.com> wrote:
>> 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
>>>> _______________________________________________
>>>> freebsd-current_at_freebsd.org mailing list
>>>> http://lists.freebsd.org/mailman/listinfo/freebsd-current
>>>> To unsubscribe, send any mail to
>>>> "freebsd-current-unsubscribe_at_freebsd.org"
>>>>
>>>
>>> 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.
>
> sorry, but the patch was not really intended to fix anything yet. it
> was just a small bit.
>
>> Typing blindly I managed to panic from kdb, and I got only this:
>>
>> KDB: enter: manual escape to debugger

Manul ecape to debugger.

>> panic: from debugger
>> cpuid = 1
>> KDB: stack backtrace:
>> panic: bufwrite: buffer is not busy???
>
> this looks like it came from ffs_bufwrite() in ufs/ffs/ffs_vfsops.c
>
>> cpuid = 1
>> KDB: enter: panic
>> exclusive sleep mutex Giant (Giant) r = 1 (0xc0725a70) locked _at_
>> /usr/src/sys/dev
>> /syscons/syscons.c:618
>>
>
> can you please setup a serial console and reproduce the panic?
>
> thanks
> max
>

No, it is not panic, I manualy paniced it because display was blank
and keyboard did not worked inside Xorg (ctr+alt+backpace didn't
work), but ctrl+alt+esc worked after some time and I blindly typed
panic, followed with enter.

-- 
Paul