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

[Kuppuswamy, Sathyanarayanan]

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