Kees Cook [off-list ref] writes:

On Thu, Oct 5, 2017 at 10:21 AM, Abdul Haleem
[off-list ref] wrote:

quoted

Hi,

CPU off on in a loop for single cpu results in kernel panic for
4.14.0-rc2-next-20170929

Machine: Power 8 PowerVM LPAR
Kernel: 4.14.0-rc2-next-20170929
gcc: 5.1.1
config : attached

Steps to recreate:
-----------------
The issue is not reproducible all the time.

The trace occurred when CPU toggle operation for cpu14 in a loop for 10
iterations.

the Faulting instruction address: 0xc00000000035465c
maps to:

0xc00000000035465c is in deactivate_slab (mm/slub.c:261).
256
257     /* Returns the freelist pointer recorded at location ptr_addr. */
258     static inline void *freelist_dereference(const struct kmem_cache *s,
259                                              void *ptr_addr)
260     {
261             return freelist_ptr(s, (void *)*(unsigned long *)(ptr_addr),
262                                 (unsigned long)ptr_addr);
263     }
264
265     static inline void *get_freepointer(struct kmem_cache *s, void *object)

This looks like slub cache corruption (a NULL pointer dereference for
the heap freelist).

Abdul, try turning on CONFIG_SLUB_DEBUG, and booting with slub_debug=FZP
on the command line.

cheers