Re: KEXEC: allocate crash note buffers at boot time v5

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 02/12/11 16:38, Jan Beulich wrote:
>> patch, Xen will give crash areas for all pcpus up to nr_cpu_ids, which
>> covers all the cases.  The worst that will happen is that some crash
>> notes do not get written if certain cpus are offline at the time of a crash.
> And did you check that nothing in the producer or consumer chain gets
> confused by this new behavior?
>
> Jan
>

/proc/vmcore reported by the kdump kernel is fine, even with extra notes
which have 0 contents (after I deliberately caused kexec_get_cpu to
report 1 more cpu than was present for testing exactly this)

The producer/consumer chain will not change.  There was a case
previously where a CPU which was present at boot and subsequently
offlined would leave crash notes with 0's in them.  Therefore, if a tool
couldn't deal with that case, it wont be able to deal with this case. 
If a tool could deal with that case, it can deal with the new case.

I would hazard a guess that most of the time, we will boot on all CPUs
and crash with all of those CPUs still up, so it is more likely that
there will be no 0'd notes.

(When I say a 0'd note, I mean a note with correct header, type and
name, but 0's in the desc)

-- 
Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
T: +44 (0)1223 225 900, http://www.citrix.com