slab/mempolicy: always use local policy from interrupt context
authorAndi Kleen <ak@linux.intel.com>
Sat, 9 Jun 2012 09:40:03 +0000 (02:40 -0700)
committerPekka Enberg <penberg@kernel.org>
Wed, 20 Jun 2012 07:01:04 +0000 (10:01 +0300)
commite7b691b085fda913830e5280ae6f724b2a63c824
tree9fbd380538f1c3fd5e36c5beeac35041351baf40
parent8c138bc00925521c4e764269db3a903bd2a51592
slab/mempolicy: always use local policy from interrupt context

slab_node() could access current->mempolicy from interrupt context.
However there's a race condition during exit where the mempolicy
is first freed and then the pointer zeroed.

Using this from interrupts seems bogus anyways. The interrupt
will interrupt a random process and therefore get a random
mempolicy. Many times, this will be idle's, which noone can change.

Just disable this here and always use local for slab
from interrupts. I also cleaned up the callers of slab_node a bit
which always passed the same argument.

I believe the original mempolicy code did that in fact,
so it's likely a regression.

v2: send version with correct logic
v3: simplify. fix typo.
Reported-by: Arun Sharma <asharma@fb.com>
Cc: penberg@kernel.org
Cc: cl@linux.com
Signed-off-by: Andi Kleen <ak@linux.intel.com>
[tdmackey@twitter.com: Rework control flow based on feedback from
cl@linux.com, fix logic, and cleanup current task_struct reference]
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: David Mackey <tdmackey@twitter.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
include/linux/mempolicy.h
mm/mempolicy.c
mm/slab.c
mm/slub.c