On Thu, Jun 16, 2016 at 8:33 AM, Josh Poimboeuf [off-list ref] wrote:

On Wed, Jun 15, 2016 at 05:28:26PM -0700, Andy Lutomirski wrote:

quoted

Currently, NR_KERNEL_STACK tracks the number of kernel stacks in a
zone.  This only makes sense if each kernel stack exists entirely in
one zone, and allowing vmapped stacks could break this assumption.

It turns out that the code for tracking kernel stack allocations in
units of pages is slightly simpler, so just switch to counting
pages.

Cc: Vladimir Davydov <redacted>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 fs/proc/meminfo.c | 2 +-
 kernel/fork.c     | 3 ++-
 mm/page_alloc.c   | 3 +--
 3 files changed, 4 insertions(+), 4 deletions(-)

You missed another usage of NR_KERNEL_STACK in drivers/base/node.c.

Thanks.

The real reason I cc'd you was so you could look at
rewind_stack_do_exit and the sneaky trick I did in no_context in the
last patch, though.  :)  Both survive objtool, but I figured I'd check
with objtool's author as well.  If there was a taint bit I could set
saying "kernel is hosed -- don't try to apply live patches any more",
I'd have extra confidence.

--Andy

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