[Crash-utility] Heads up: possible 2.6.31 kdump and crash utility failures

You may have seen this discussion re: 2.6.31 kdump failures on the kexec(a)lists.infradead.org mailing list: Kdump issue with percpu_alloc=lpage (Was:Re: crash_notes posted to kexec-tools) http://lists.infradead.org/pipermail/kexec/2009-October/003587.html or saw Vivek's subsequent post to LKML to address it: [PATCH] Fix kdump failure if booted with percpu_alloc=page http://lkml.org/lkml/2009/11/19/214 Basically if a 2.6.31 or later kernel is: (1) configured with CONFIG_NEED_MULTIPLE_NODES, and (2) the system actually has multiple NUMA nodes, then it will use vmalloc space for its percpu data. In that case, the 2.6.31 kernel uses the "lpage" percpu memory allocator (subsequently renamed the "page" allocator) instead of the traditional "embed" percpu memory allocator. At least on x86_64, this will cause the the crash utility to fail during initialization, because it tries to read vmalloc memory prior to having set itself up to be able to walk page tables. Prior to 4.1.1, it would fail with this error message: crash: read error: kernel virtual address: ffffc9000000e2f8 type: cpu number (per_cpu) With 4.1.1 -- which quietly accepts the readmem failure above -- it fails later on with these two error messages: crash: cannot determine idle task addresses from init_tasks[] or runqueues[] crash: cannot resolve "init_task_union" I believe that this only affects x86_64. I am testing a fix for it, which I will put in a new crash release in short order. Dave