Chandru wrote:
Dave Anderson wrote:
As I suggested before, you're going to have to determine why
the tasklist[i] is bogus. The first things to determine are:
(1) what "nr_cpus" was calculated to be, and
(2) whether the SMP and PER_CPU_OFF flags are set in kt->flags.
If those variables/settings make sense, then presumably the
problem is in the determination of the per-cpu offset values.
That's done in a machine-specific way, so I can't help you
without knowing what architecture you're dealing with, not
to mention what kernel version, or whether it's configured
CONFIG_SMP or not, and whether you can run crash on the live
system that generated the dumpfile.
Dave
The machine is a ppc64 box with a RHEL5.1 based SMP kernel. nr_cpus
is equal to '2' in get_idle_threads() , but the system actually has 14
cpus and 12 of them were offline when a vmcore was collected. The
kt->__per_cpu_offset[12 & 13 ] have per cpu offset values where as
kt->__per_cpu_offset[0 to 11] = 0. I changed kt->__per_cpu_offset[i]
in ppc64_paca_init() to kt->__per_cpu_offset[cpus] and that started
crash. But backtrace 'bt' exited with segmentation fault . Looking
further the code in get_netdump_regs_ppc64()
if (nd->num_prstatus_notes > 1)
{
note = (Elf64_Nhdr *)
nd->nt_prstatus_percpu[bt->tc->processor];
}
had bt->tc->processor as '12'. I changed it to '0' and that gave the
backtrace.
Regards,
Chandru
OK, it sounds like the kt->cpus value should have been set to 14 by
ppc64_paca_init().
And it appears that when kdump created the vmcore, it only installs two
NT_PRSTATUS
sections. And that being the case, the consumer of the ELF header has
to figure out what
cpu that each NT_PRSTATUS section one belongs to. I'm not sure how that
can be
determined.
And it seems that there may be other oddities that may crop up when running
other commands. Or maybe not...
I'm going to ultimately defer this back to the IBM for resolution.
haren@xxxxxxxxxx
<https://www.redhat.com/mailman/options/crash-utility/haren--at--us.ibm.com>
wrote the ppc64.c file, and he is on this mailing
list. But would it be possible for you to make the vmlinux/vmcore pair
available to me? (If so, you can send me the particulars off-line)
Thanks,
Dave
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