On 12/07/2012 01:09 AM, Toshi Kani wrote: > On Fri, 2012-12-07 at 00:52 +0800, Jiang Liu wrote: >> On 12/07/2012 12:31 AM, Toshi Kani wrote: >>> On Fri, 2012-12-07 at 00:25 +0800, Jiang Liu wrote: >>>> On 12/07/2012 12:03 AM, Toshi Kani wrote: >>>>> On Fri, 2012-12-07 at 00:00 +0800, Jiang Liu wrote: >>>>>> On 11/29/2012 02:41 AM, Toshi Kani wrote: >>>>>>> On Wed, 2012-11-28 at 19:05 +0800, Hanjun Guo wrote: >>> : >>>>>>> Yes, sharing idea is good. :) I do not know if we need all 6 steps (I >>>>>>> have not looked at all your changes yet..), but in my mind, a hot-plug >>>>>>> operation should be composed with the following 3 phases. >>>>>>> >>>>>>> 1. Validate phase - Verify if the request is a supported operation. All >>>>>>> known restrictions are verified at this phase. For instance, if a >>>>>>> hot-remove request involves kernel memory, it is failed in this phase. >>>>>>> Since this phase makes no change, no rollback is necessary to fail. >>>>>>> >>>>>>> 2. Execute phase - Perform hot-add / hot-remove operation that can be >>>>>>> rolled-back in case of error or cancel. >>>>>>> >>>>>>> 3. Commit phase - Perform the final hot-add / hot-remove operation that >>>>>>> cannot be rolled-back. No error / cancel is allowed in this phase. For >>>>>>> instance, eject operation is performed at this phase. >>>>>> Hi Toshi, >>>>>> There are one more step needed. Linux provides sysfs interfaces to >>>>>> online/offline CPU/memory sections, so we need to protect from concurrent >>>>>> operations from those interfaces when doing physical hotplug. Think about >>>>>> following sequence: >>>>>> Thread 1 >>>>>> 1. validate conditions for hot-removal >>>>>> 2. offline memory section A >>>>>> 3. online memory section A >>>>>> 4. offline memory section B >>>>>> 5 hot-remove memory device hosting A and B. >>>>> >>>>> Hi Gerry, >>>>> >>>>> I agree. And I am working on a proposal that tries to address this >>>>> issue by integrating both sysfs and hotplug operations into a framework. >>>> Hi Toshi, >>>> But the sysfs for CPU and memory online/offline are platform independent >>>> interfaces, and the ACPI based hotplug is platform dependent interfaces. I'm not >>>> sure whether it's feasible to merge them. For example we still need offline interface >>>> to stop using faulty CPUs on platform without physical hotplug capabilities. >>>> We have solved this by adding a "busy" flag to the device, so the sysfs >>>> will just return -EBUSY if the busy flag is set. >>> >>> I am making the framework code platform-independent so that it can >>> handle both cases. Well, I am still prototyping, so hopefully it will >>> work. :) >> Do you mean implementing a framework to manage hotplug of any type of devices? >> That sounds like a huge plan:) >> >> Otherwise there may be a gap. CPU online/offline interface deals with logical >> CPU, and hotplug driver deals with physical devices(processor). They may be different >> by related objects. > > Actually it is not a huge plan. The framework I am thinking of is to > enable a hotplug sequencer something analogous to do_initcalls() at the > boot sequence. I am not doing any huge re-work. That said, I am > currently testing my theory, so I won't promise anything, either. :) Please do give us an update when you get any progress:) > > Thanks, > -Toshi > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>