Re: [PATCH 2/5 V2] PCI: pciehp: check and wait port status out of DPC before handling DLLSC and PDC

[Sinan Kaya]

On 9/28/2020 7:10 AM, Sinan Kaya wrote:
> On 9/27/2020 10:01 PM, Zhao, Haifeng wrote:
>> Sinan,
>>    I explained the reason why locks don't protect this case in the patch description part. 
>> Write side and read side hold different semaphore and mutex.
>>
> I have been thinking about it some time but is there any reason why we
> have to handle all port AER/DPC/HP events in different threads?
> 
> Can we go to single threaded event loop for all port drivers events?
> 
> This will require some refactoring but it wlll eliminate the lock
> nightmares we are having.
> 
> This means no sleeping. All sleeps need to happen outside of the loop.
> 
> I wanted to see what you all are thinking about this.
> 
> It might become a performance problem if the system is
> continuously observing a hotplug/aer/dpc events.
> 
> I always think that these should be rare events.

If restructuring would be too costly, the preferred solution should be
to fix the locks in hotplug driver rather than throwing there a random
wait call.