>-----Original Message----- >From: Bryce Harrington [mailto:bryce@xxxxxxxx] >Sent: Tuesday, May 02, 2006 10:04 AM >To: Mary Edie Meredith >Cc: Raj, Ashok; Hotplug SIG; lhcs-devel@xxxxxxxxxxxxxxxxxxxxx >Subject: Re: Hotplug CPU issue? > >On Tue, May 02, 2006 at 09:59:18AM -0700, Mary Edie Meredith wrote: >> So that means that an implementation _can have an online file, even >> though the corresponding cpu is not able to offline. Sounds like having >> an online file in sysfs isn't a sure indication of an "off-lineable" cpu >> after all. > >Well, possibly, unless that situation is considered a bug. Not necessarily. Say for e.g there may be platform interrupts that could be only migrated to certain cpus. Say on a 8way system you have cpus 0-3 that can take a platform interrupts. And 4-7 cannot handle it, when you remove each cpu one by one, and you run into the last cpu that can handle the interrupt and cannot be moved anywhere, the operation will fail. The result of the echo command should tell if it succeded or not. > >Mary, have you seen any sort of specification for the cpu hotplug design >that indicates when the online file should/shouldn't be present, or >anything regarding for a given architecture, how to determine what cpu's >can be onlined/offlined? It started with some power stuff, that depending on what fw is loaded (I might word it wrong) cpu offlining may not be supported even though kernel is compiled with support to offline. Then you see the online file missing. We just extended the same for other types as well, for e.g If bsp cannot be removed If CPEI (on ia64) cannot be migrated to another cpu other than what ACPI told us its associated with etc. > >Bryce
