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. :) 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>