lkml.org 
[lkml]   [2015]   [Aug]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 7/7] ipmi/kcs: Don't run the KCS state machine when it is KCS_IDLE
On 08/23/2015 08:52 PM, 河合英宏 / KAWAI,HIDEHIRO wrote:
>> From: Corey Minyard [mailto:tcminyard@gmail.com] On Behalf Of Corey Minyard
>>
>> On 08/17/2015 09:54 PM, 河合英宏 / KAWAI,HIDEHIRO wrote:
>>>> From: Corey Minyard [mailto:tcminyard@gmail.com] On Behalf Of Corey Minyard
>>>>
>>>> This patch will break ATN handling on the interfaces. So we can't do this.
>>> I understand. So how about doing like this:
>>>
>>> /* All states wait for ibf, so just do it here. */
>>> - if (!check_ibf(kcs, status, time))
>>> + if (kcs->state != KCS_IDLE && !check_ibf(kcs, status, time))
>>> return SI_SM_CALL_WITH_DELAY;
>>>
>>> I think it is not necessary to wait IBF when the state is IDLE.
>>> In this way, we can also handle the ATN case.
>> I think it would be more reliable to go up a level and add a timeout.
> It may be so, but we should address this issue separately (at least
> I think above solution reasonably solves the issue).
>
> This issue happens after all queued messages are processed or dropped
> by timeout. There is no current message. So what should we set
> a timeout against? We can add a timeout into my new flush_messages(),
> but that is meaningful only in panic context. That doesn't help
> in normal context; we would perform a busy loop of smi_event_handler()
> and schedule() in ipmi_thread().

I'm a little confused here. Is the problem that the ATN bit is stuck
high? If so, it's going to be really hard to work around this without
breaking ATN handling.

-corey

>
> Regards,
>
> Hidehiro Kawai
>
>> One should
>> be there, anyway. I thought they were all covered, but I may have missed
>> something.
>>
>> -corey
>>
>>> Regards,
>>>
>>> Hidehiro Kawai
>>> Hitachi, Ltd. Research & Development Group
>>>
>>>> It's going to be extremely hard to recover if the BMC is not working
>>>> correctly when a panic happens. I'm not sure what can be done, but if
>>>> you can fix it another way it would be good.
>>>>
>>>> -corey
>>>>
>>>> On 07/27/2015 12:55 AM, Hidehiro Kawai wrote:
>>>>> If a BMC is unresponsive for some reason, it ends up completing
>>>>> the requested message as an error, then kcs_event() is called once
>>>>> to advance the state machine. However, since the BMC is
>>>>> unresponsive now, the status of the KCS interface may not be
>>>>> idle. As the result, the state machine can continue to run and
>>>>> comsume CPU time indefinitely even if there is no more request
>>>>> message. Moreover, if this happens in run-to-completion mode
>>>>> (i.e. context of panic_event()), the kernel hangs up.
>>>>>
>>>>> To fix this problem, this patch ignores kcs_event() call if there
>>>>> is no request message to be processed.
>>>>>
>>>>> Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
>>>>> ---
>>>>> drivers/char/ipmi/ipmi_kcs_sm.c | 4 ++++
>>>>> 1 file changed, 4 insertions(+)
>>>>>
>>>>> diff --git a/drivers/char/ipmi/ipmi_kcs_sm.c b/drivers/char/ipmi/ipmi_kcs_sm.c
>>>>> index 8c25f59..0e187fb 100644
>>>>> --- a/drivers/char/ipmi/ipmi_kcs_sm.c
>>>>> +++ b/drivers/char/ipmi/ipmi_kcs_sm.c
>>>>> @@ -353,6 +353,10 @@ static enum si_sm_result kcs_event(struct si_sm_data *kcs, long time)
>>>>> if (kcs_debug & KCS_DEBUG_STATES)
>>>>> printk(KERN_DEBUG "KCS: State = %d, %x\n", kcs->state, status);
>>>>>
>>>>> + /* We don't want to run the state machine when the state is IDLE */
>>>>> + if (kcs->state == KCS_IDLE)
>>>>> + return SI_SM_IDLE;
>>>>> +
>>>>> /* All states wait for ibf, so just do it here. */
>>>>> if (!check_ibf(kcs, status, time))
>>>>> return SI_SM_CALL_WITH_DELAY;
>>>>>
>>>>>



\
 
 \ /
  Last update: 2015-08-24 18:21    [W:0.142 / U:1.056 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site