On Wed, Dec 21, 2016 at 11:57 AM, Pratyush Anand <panand at redhat.com> wrote: > > > On Wednesday 21 December 2016 08:56 AM, Xunlei Pang wrote: >> >> 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. > > > Yes, yes..I agree, I meant that the above info is just indicative. May be > "might have been" could be better word than "would have been" in the above > info print message. > > >> >> 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. > > > Hummm..this is certainly possible. But can we do much even when we get the > info that the PT_NOTE was compromised by user space? > If doing this, kexec should be re-forked each time when online/offline. I think it is not worth to do so just for suppressing some warning. > Therefore, I am of the view that if at all we are concerned about number of > warning messages in case of multiple offline cpu, then we can just print the > total number of NULL PT_NOTE at the end of loop. > Yes, I think it is a good idea. NULL PT_NOTES are only caused by offlne cpu, it is better to change the waring to info Thx, Pingfan
