> From: Corey Minyard [mailto:[email protected]] 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.
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 <[email protected]>
> > ---
> > 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;
> >
> >
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