Re: A udev rule to serve the change event of ACPI container?

[joeyli]

Hi Yasuaki,  

On Fri, Jul 14, 2017 at 10:44:14PM +0800, joeyli wrote:
> On Fri, Jul 14, 2017 at 10:37:13AM +0200, Michal Hocko wrote:
> > On Thu 13-07-17 20:45:21, Joey Lee wrote:
> > > On Thu, Jul 13, 2017 at 09:06:19AM +0200, Michal Hocko wrote:
> > > > On Thu 13-07-17 14:58:06, Joey Lee wrote:
> > [...]
> > > > > If BIOS emits ejection event for a ACPI0004 container, someone needs
> > > > > to handle the offline/eject jobs of container. Either kernel or user
> > > > > space.
> > > > > 
> > > > > Only sending uevent to individual child device can simplify udev rule,
> > > > > but it also means that the kernel needs to offline/eject container
> > > > > after all children devices are offlined.
> > > > 
> > > > Why cannot kernel send this eject command to the BIOS if the whole
> > > > container is offline? If it is not then the kernel would send EBUSY to
> > > 
> > > Current kernel container hot-remove process:
> > > 
> > >   BIOS -> SCI event -> Kernel ACPI -> uevent -> userland
> > >               
> > > Then, kernel just calls _OST to expose state to BIOS, then process is
> > > stopped. Kernel doesn't wait there for userland to offline each child
> > > devices. Either BIOS or userland needs to trigger the container
> > > ejection.
> > > 
> > > > container is offline? If it is not then the kernel would send EBUSY to
> > > > the BIOS and BIOS would have to retry after some timeout. Or is it a
> > > 
> > > The d429e5c122 patch is merged to mainline. So kernel will send
> > > DEVICE_BUSY to BIOS after it emits uevent to userland. BIOS can choice
> > > to apply the retry approach until OS returns process failure exactly or
> > > BIOS timeout.
> > > 
> > > > problem that currently implemented BIOS firmwares do not implement this
> > > > retry?
> > > 
> > > Yes, we should consider the behavior of old BIOS. Old BIOS doesn't
> > > retry/resend the ejection event. So kernel or userland need to take the
> > > retry job. Obviously userland runs the retry since the caa73ea15 patch
> > > is merged.
> > > 
> > > IMHO there have two different expectation from user space application.
> > > 
> > > Applications like DVD player or Burner expect that kernel should
> > > info userspace for the ejection, then application can do their cleaning
> > > job and re-trigger ejection from userland.
> > 
> > I am not sure I understand the DVD example because I do not see how it
> > fits into the container and online/offline scenario.
> >
> 
> At least Yasuaki raised similar behavior for container in 2013.
> It's similar to the DVD player case, user space application needs
> to do something then trigger children offline and ejection of
> container.
> 
> Base on Yasuaki's explanation, the reason of that he requested the
> userland ejection approach is that he got memory hot-remove problem
> in 2013. Maybe his problem is already fixed by your patches in current
> mainline.
> 
> Hi Yasuaki, could you please check that your memory hot-remove problem
> is fixed on mainline kernel?  
> 
> If Yasuaki's issue is already fixed, then we should consider to let
> kernel does the container hot-remove transparently. 

Could you please help to check that your memory hot-remove problem in 2013
is fixed on mainline kernel?  

Thanks a lot!
Joey Lee