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

On 9/28/20 9:43 AM, Sinan Kaya wrote:
> 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.
Since the current race condition is detected between DPC and
hotplug, I recommend synchronizing them.

Sathyanarayanan Kuppuswamy
Linux Kernel Developer

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