RE: [PATCH 7/7] ipmi/kcs: Don't run the KCS state machine when it is KCS_IDLE
> From: Corey Minyard [mailto:tcminy...@gmail.com] On Behalf Of Corey Minyard > > On 08/24/2015 10:53 PM, 河合英宏 / KAWAI，HIDEHIRO wrote: > >> From: Corey Minyard [mailto:tcminy...@gmail.com] On Behalf Of Corey Minyard > >> > >> On 08/23/2015 08:52 PM, 河合英宏 / KAWAI，HIDEHIRO wrote: > From: Corey Minyard [mailto:tcminy...@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:tcminy...@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. > > Sorry for my insufficient explanation. I assume the case where > > IBF bit is always 1. I don't know what happens when > > BMC hangs up, but I guess IBF stays in 1 because my server's > > BMC behaves as such while rebooting. > > > Ok, your patch above makes sense, then. IBF is irrelevant when in idle > state, > so ignore it then, and then in your case it will return KCS_IDLE and > cause that > operation to complete. I'm ok with the patch you posted above, I think > it will > work correctly and solve the problem. > > I would like a detailed comment, though, so people (forgetful people > like me :) > can figure out why it is there. Sure. I'll post the revised version with detailed comment and description later including PATCH 6/7. Thanks, Hidehiro Kawai
Re: [PATCH 7/7] ipmi/kcs: Don't run the KCS state machine when it is KCS_IDLE
On 08/24/2015 10:53 PM, 河合英宏 / KAWAI，HIDEHIRO wrote: >> From: Corey Minyard [mailto:tcminy...@gmail.com] On Behalf Of Corey Minyard >> >> On 08/23/2015 08:52 PM, 河合英宏 / KAWAI，HIDEHIRO wrote: From: Corey Minyard [mailto:tcminy...@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:tcminy...@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. > Sorry for my insufficient explanation. I assume the case where > IBF bit is always 1. I don't know what happens when > BMC hangs up, but I guess IBF stays in 1 because my server's > BMC behaves as such while rebooting. > Ok, your patch above makes sense, then. IBF is irrelevant when in idle state, so ignore it then, and then in your case it will return KCS_IDLE and cause that operation to complete. I'm ok with the patch you posted above, I think it will work correctly and solve the problem. I would like a detailed comment, though, so people (forgetful people like me :) can figure out why it is there. I'd also like to save this one until 4.4 to give it some time in linux-next for people to find issues. Thanks, -corey -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
RE: [PATCH 7/7] ipmi/kcs: Don't run the KCS state machine when it is KCS_IDLE
> From: Corey Minyard [mailto:tcminy...@gmail.com] On Behalf Of Corey Minyard > > On 08/23/2015 08:52 PM, 河合英宏 / KAWAI，HIDEHIRO wrote: > >> From: Corey Minyard [mailto:tcminy...@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:tcminy...@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. Sorry for my insufficient explanation. I assume the case where IBF bit is always 1. I don't know what happens when BMC hangs up, but I guess IBF stays in 1 because my server's BMC behaves as such while rebooting. 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 > > --- > > 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; > > > >
Re: [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:tcminy...@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:tcminy...@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 > --- > 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; > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
RE: [PATCH 7/7] ipmi/kcs: Don't run the KCS state machine when it is KCS_IDLE
> From: Corey Minyard [mailto:tcminy...@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:tcminy...@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(). 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 > >>> --- > >>> 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; > >>> > >>>
Re: [PATCH 7/7] ipmi/kcs: Don't run the KCS state machine when it is KCS_IDLE
On 08/17/2015 09:54 PM, 河合英宏 / KAWAI，HIDEHIRO wrote: >> From: Corey Minyard [mailto:tcminy...@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. 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 >>> --- >>> 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; >>> >>> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
RE: [PATCH 7/7] ipmi/kcs: Don't run the KCS state machine when it is KCS_IDLE
> From: Corey Minyard [mailto:tcminy...@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.
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
> > ---
> > 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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Re: [PATCH 7/7] ipmi/kcs: Don't run the KCS state machine when it is KCS_IDLE
This patch will break ATN handling on the interfaces. So we can't do this. 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 > --- > 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; > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
