Re: [Crash-utility] crash aborts with cannot determine idle task
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