Re: [PATCH 2/7] xen/events: don't unmask an event channel when an eoi is pending

Jürgen Groß
2021-02-08T10:33:39Z

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On 08.02.21 11:06, Jan Beulich wrote:
> On 06.02.2021 11:49, Juergen Gross wrote:
>> @@ -1798,6 +1818,29 @@ static void mask_ack_dynirq(struct irq_data *data)
>> ack_dynirq(data);
>> }
>>
>> +static void lateeoi_ack_dynirq(struct irq_data *data)
>> +{
>> + struct irq_info *info = info_for_irq(data->irq);
>> + evtchn_port_t evtchn = info ? info->evtchn : 0;
>> +
>> + if (VALID_EVTCHN(evtchn)) {
>> + info->eoi_pending = true;
>> + mask_evtchn(evtchn);
>> + }
>> +}
>> +
>> +static void lateeoi_mask_ack_dynirq(struct irq_data *data)
>> +{
>> + struct irq_info *info = info_for_irq(data->irq);
>> + evtchn_port_t evtchn = info ? info->evtchn : 0;
>> +
>> + if (VALID_EVTCHN(evtchn)) {
>> + info->masked = true;
>> + info->eoi_pending = true;
>> + mask_evtchn(evtchn);
>> + }
>> +}
>> +
>> static int retrigger_dynirq(struct irq_data *data)
>> {
>> evtchn_port_t evtchn = evtchn_from_irq(data->irq);
>> @@ -2023,8 +2066,8 @@ static struct irq_chip xen_lateeoi_chip __read_mostly = {
>> .irq_mask = disable_dynirq,
>> .irq_unmask = enable_dynirq,
>>
>> - .irq_ack = mask_ack_dynirq,
>> - .irq_mask_ack = mask_ack_dynirq,
>> + .irq_ack = lateeoi_ack_dynirq,
>> + .irq_mask_ack = lateeoi_mask_ack_dynirq,
>>
>> .irq_set_affinity = set_affinity_irq,
>> .irq_retrigger = retrigger_dynirq,
>>
>
> Unlike the prior handler the two new ones don't call ack_dynirq()
> anymore, and the description doesn't give a hint towards this
> difference. As a consequence, clear_evtchn() also doesn't get
> called anymore - patch 3 adds the calls, but claims an older
> commit to have been at fault. _If_ ack_dynirq() indeed isn't to
> be called here, shouldn't the clear_evtchn() calls get added
> right here?

There was clearly too much time between writing this patch and looking
at its performance impact. :-(

Somehow I managed to overlook that I just introduced the bug here. This
OTOH explains why there are not tons of complaints with the current
implementation. :-)

Will merge patch 3 into this one.

Juergen

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