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