Messages in this thread | | | Date | Wed, 4 Jun 2014 09:46:49 -0400 | From | Vivek Goyal <> | Subject | Re: [PATCH] powerpc, kexec: Fix "Processor X is stuck" issue during kexec from ST mode |
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On Wed, Jun 04, 2014 at 08:09:25AM +1000, Benjamin Herrenschmidt wrote: > On Wed, 2014-06-04 at 01:58 +0530, Srivatsa S. Bhat wrote: > > Yep, that makes sense. But unfortunately I don't have enough insight into > > why exactly powerpc has to online the CPUs before doing a kexec. I just > > know from the commit log and the comment mentioned above (and from my own > > experiments) that the CPUs will get stuck if they were offline. Perhaps > > somebody more knowledgeable can explain this in detail and suggest a proper > > long-term solution. > > > > Matt, Ben, any thoughts on this? > > The problem is with our "soft offline" which we do on some platforms. When we > offline we don't actually send the CPUs back to firmware or anything like that. > > We put them into a very low low power loop inside Linux. > > The new kernel has no way to extract them from that loop. So we must re-"online" > them before we kexec so they can be passed to the new kernel normally (or returned > to firmware like we do on powernv).
Srivatsa,
Looks like your patch has been merged.
I don't like the following change in arch independent code.
/* * migrate_to_reboot_cpu() disables CPU hotplug assuming that * no further code needs to use CPU hotplug (which is true in * the reboot case). However, the kexec path depends on using * CPU hotplug again; so re-enable it here. */ cpu_hotplug_enable();
As it is very powerpc specific requirement, can you enable hotplug in powerpc arch dependent code as a short term solution.
Ideally one needs to fix the requirement of online all cpus in powerpc as a long term solution and then get rid of hotplug enable call.
Thanks Vivek
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