On Wed, 2006-02-22 at 15:31 -0800, Haren Myneni wrote: > Haren Myneni wrote: > > > > > > > crash-utility-bounces@xxxxxxxxxx wrote on 02/22/2006 07:31:43 AM: > > > > > Rachita Kothiyal wrote: > > > > > > > > > > > > Rachita Kothiyal wrote: > > > > > > > > > > > > > > > > > > This happens in get_idle_threads() when perusing the runqueues > > array, > > > > > where each per-cpu runqueue data structure contains a pointer to the > > > > > idle (swapper) task for that CPU. Now, this process requires > > that the > > > > > per-cpu address manipulations are working correctly in order to > > find the > > > > > each cpu's runqueue data structure. It looks like the ppc64 change > > > > > for per-cpu data accesses is suspect here: > > > > > > > > > > > Fix to recognize post-2.6.15 ppc64 kernels moving the > > per_cpu_offsets > > > > > > to the "paca" structure. Without this patch, crash fails with the > > > > > > following error messages: "crash: cannot determine idle task > > addresses > > > > > > from init_tasks[] or runqueues[]" and "crash: cannot resolve > > > > > > init_task_union". (pbadari@xxxxxxxxxx) > > > > > > > > > > > > > Right, but I thought this patch fixed this problem. > > > > (I am using crash-4.0-2.21, and it includes this patch) > > > > > > Right -- me too... ;-) > > > > Badari tested his patch on live system. He can give more information > > anyway. > > > > However, I used his patch for testing PPC64 vmcore before I post my > > patch. Did not see any issue when invoking crash tool. Tested on > > 2.6.16-rc2-gi9. > > > > I will also verify if I have the same vmcore. > > > > Thanks > > Haren > > > Dave, > > I used Badari's patch (first version) for my testing on PPC64 kdump > vmcore. Later, this patch was changed to use paca[CPU#].hw_cpu_id to > determine whether the CPU exists (CPU hotplug case). The reason it > failed on vmcore is, when the kdump boot happens, this hw_cpu_id is set > to -1 for secondary cpus when they stopped. Hence, not setting > per_cpu_offset for these CPUs and causing this issue. > > Instead of looking for hw_cpu_id, this patch will look for the > corresponding data_offset. If 0, means CPU does not exists. > > Rachita, please let us know if still an issue. Badari, is there any > issue with this patch? Haren, Yes. My first version of the patch did exactly this. Later, while discussing with you we decided that checking for "-1" for CPU ID is the right thing to identify the presence of the CPU. Yep. you are right on kdump boot, you do set cpuid to -1 when they are stopped. So, I guess I am okay with your fix. Thanks, Badari
