Re: [PATCH] cxl/events: Return IRQ_NONE when no event is pending

[Li Ming <ming.li@zohomail.com>]

在 2026/9/8 02:48, Jonathan Cameron 写道:
> On Sun,  6 Sep 2026 21:27:05 +0530
> Shaikh Kamaluddin <shaikhkamal2012@gmail.com> wrote:
>
>> CXL event interrupts may share an MSI/MSI-X vector with other event
>> logs or device features. Consequently, cxl_event_thread() is registered
>> with IRQF_SHARED and must determine whether an interrupt belongs to the
>> event-log facility.
>>
>> The handler masks the Device Event Status register to the event logs
>> supported by the driver. However, when no supported status bit is set,
>> it exits the processing loop and still returns IRQ_HANDLED.
>>
>> Track whether at least one supported event status bit was observed.
>> Return IRQ_NONE when there was no event to service, while continuing to
>> return IRQ_HANDLED after processing one or more event logs.
> What is the practical result of this change?
> I think it will only affect the spurious interrupt detection so
> to me it looks like a cleanup rather than a fix.  Is there
> any path by which we actually lose interrupts as a result of this?
>
>> Fixes: a49aa8141b65 ("cxl/mem: Wire up event interrupts")
>>
> No blank lines in tag blocks.  There are a number of tools that rely
> on there not being any and as such there are also scripts that run
> on various upstream trees that will send us annoying emails if this
> blank line is still here!  I'm not sure why this mistake in patch
> formatting is so common as there are plenty of docs without the
> blank lines!
>
>> Signed-off-by: Shaikh Kamaluddin <shaikhkamal2012@gmail.com>
> A suggestion for an alternative implementation below.
>
>> ---
>>   drivers/cxl/pci.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
>> index c7c91e8dc51d..8b560cae91f2 100644
>> --- a/drivers/cxl/pci.c
>> +++ b/drivers/cxl/pci.c
>> @@ -515,6 +515,7 @@ static irqreturn_t cxl_event_thread(int irq, void *id)
>>   	struct cxl_dev_id *dev_id = id;
>>   	struct cxl_dev_state *cxlds = dev_id->cxlds;
>>   	struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlds);
>> +	bool handled = false;
>>   	u32 status;
>>   
>>   	do {
>> @@ -527,11 +528,13 @@ static irqreturn_t cxl_event_thread(int irq, void *id)
>>   		status &= CXLDEV_EVENT_STATUS_ALL;
>>   		if (!status)
> 			return IRQ_NONE;
>
> And don't need the other changes.

Hi Jonathan,


I think we should not return IRQ_NONE here, because the loop could run 
multiple times untill no event record, so we always get a status with 
0x0 value in the last loop. In that case, we still need to return 
IRQ_HANDLED.


Ming

>
>>   			break;
>> +
>> +		handled = true;
>>   		cxl_mem_get_event_records(mds, status);
>>   		cond_resched();
>>   	} while (status);
>>   
>> -	return IRQ_HANDLED;
>> +	return handled ? IRQ_HANDLED : IRQ_NONE;
>>   }
>>   
>>   static int cxl_event_req_irq(struct cxl_dev_state *cxlds, u8 setting)
>>
>> base-commit: 7098e9cd98a05c0c5de2fae0c2465f9d966fdd07
>> prerequisite-patch-id: 92e40cd60a697020faac475dcc77ba63b33434ea
>> prerequisite-patch-id: 10027ad5d9aed85806047f807b3a76273b6c4a77