On Mon 24-07-17 17:29:21, Joey Lee wrote: > On Mon, Jul 24, 2017 at 10:57:02AM +0200, Michal Hocko wrote: > > On Wed 19-07-17 17:09:10, Joey Lee wrote: > > > On Mon, Jul 17, 2017 at 11:05:25AM +0200, Michal Hocko wrote: > > [...] > > > > The problem I have with this expectation is that userspace will never > > > > have a good atomic view of the whole container. So it can only try to > > > > > > I agreed! > > > > > > Even a userspace application can handle part of offline jobs. It's > > > still possible that other kernel/userland compenents are using the > > > resource in container. > > > > > > > eject and then hope that nobody has onlined part of the container. > > > > If you emit offline event to the userspace the cleanup can be done and > > > > after the last component goes offline then the eject can be done > > > > atomically. > > > > > > The thing that we didn't align is how does kernel maintains the flag > > > of ejection state on container. > > > > Why it cannot be an attribute of the container? The flag would be set > > when the eject operation is requested and cleared when either the > > operation is successful (all parts offline and eject operation acked > > by the BIOS) or it is terminated. > > > > For the success case, yes, we can clear the flag when the _EJ0 of container > is success. But for the fail case, we don't know when the operation is > terminated. Hmm, this is rather strange. What is the BIOS state in the meantime? Let's say it doesn't retry. Does it wait for the OS for ever? > > [...] > > > Base on the above figure, if userspace didn't do anything or it > > > just performs part of offline jobs. Then the container's [eject] > > > state will be always _SET_ there, and kernel will always check > > > the the latest child offline state when any child be offlined > > > by userspace. > > > > What is a problem about that? The eject is simply in progress until all > > is set. Or maybe I just misunderstood. > > > > I agree, but it's only for success case. For fail case, kernel can not > wait forever. Can we? Well, this won't consume any additional resources so I wouldn't be all that worried. Maybe we can reset the flag as soon as somebody tries to online some part of the container? -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
