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. :) Thanks, -Toshi -- 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
