[PATCHv2 2/2] [fs] proc/vmcore: check the dummy place holder for offline cpu to avoid warning

Xunlei Pang xpang at redhat.com
Tue Dec 20 19:26:21 PST 2016

On 12/20/2016 at 11:38 PM, Pratyush Anand wrote:
> On Monday 19 December 2016 08:10 AM, Dave Young wrote:
>> Hi, Pingfan
>> On 12/19/16 at 10:08am, Pingfan Liu wrote:
>>> > kexec-tools always allocates program headers for present cpus. But
>>> > when crashing, offline cpus have dummy headers. We do not copy these
>>> > dummy notes into ELF file, also have no need of warning on them.
>> I still think it is not worth such a fix, if you feel a lot of warnings
>> in case large cpu numbers, I think you can change the pr_warn to
>> pr_warn_once, we do not care the null cpu notes if it has nothing bad
>> to the vmcore.
> I agree. Warning is more like information here. May be, we can count the number of times real_sz was 0, and then can print an info at the end in stead of warning, like..."N number of CPUs would have been offline, PT_NOTE entries was absent for them."

Well, OTOH the warning may also be due to some user-space misuse, we can't distinguish that without extra information added.

Another possible user-space fix would be: Firstly fix kexec-tools to add notes only for online cpus,
then utilize udev rules(cpu online/offline events) to automatically trigger kdump kernel reload.


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