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Message-ID: <50C0CD4A.90101@gmail.com> Date: Fri, 07 Dec 2012 00:52:26 +0800 From: Jiang Liu <liuj97@...il.com> To: Toshi Kani <toshi.kani@...com> CC: Hanjun Guo <guohanjun@...wei.com>, Vasilis Liaskovitis <vasilis.liaskovitis@...fitbricks.com>, linux-acpi@...r.kernel.org, isimatu.yasuaki@...fujitsu.com, wency@...fujitsu.com, rjw@...k.pl, lenb@...nel.org, gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org, Tang Chen <tangchen@...fujitsu.com> Subject: Re: [RFC PATCH v3 0/3] acpi: Introduce prepare_remove device operation 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. > > Thanks, > -Toshi > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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