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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>
This commit is contained in:
Andi Kleen 2012-06-09 02:40:03 -07:00 committed by Pekka Enberg
parent 8c138bc009
commit e7b691b085
4 changed files with 11 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/mempolicy.h
View File

@ -215,7 +215,7 @@ extern struct zonelist *huge_zonelist(struct vm_area_struct *vma,
extern bool init_nodemask_of_mempolicy(nodemask_t *mask);
extern bool mempolicy_nodemask_intersects(struct task_struct *tsk,
const nodemask_t *mask);
extern unsigned slab_node(struct mempolicy *policy);
extern unsigned slab_node(void);
extern enum zone_type policy_zone;

8
mm/mempolicy.c
View File

@ -1602,8 +1602,14 @@ static unsigned interleave_nodes(struct mempolicy *policy)
* task can change it's policy. The system default policy requires no
* such protection.
*/
unsigned slab_node(struct mempolicy *policy)
unsigned slab_node(void)
{
struct mempolicy *policy;
if (in_interrupt())
return numa_node_id();
policy = current->mempolicy;
if (!policy || policy->flags & MPOL_F_LOCAL)
return numa_node_id();

4
mm/slab.c
View File

@ -3310,7 +3310,7 @@ static void *alternate_node_alloc(struct kmem_cache *cachep, gfp_t flags)
if (cpuset_do_slab_mem_spread() && (cachep->flags & SLAB_MEM_SPREAD))
nid_alloc = cpuset_slab_spread_node();
else if (current->mempolicy)
nid_alloc = slab_node(current->mempolicy);
nid_alloc = slab_node();
if (nid_alloc != nid_here)
return ____cache_alloc_node(cachep, flags, nid_alloc);
return NULL;
@ -3342,7 +3342,7 @@ static void *fallback_alloc(struct kmem_cache *cache, gfp_t flags)
retry_cpuset:
cpuset_mems_cookie = get_mems_allowed();
zonelist = node_zonelist(slab_node(current->mempolicy), flags);
zonelist = node_zonelist(slab_node(), flags);
retry:
/*

2
mm/slub.c
View File

@ -1617,7 +1617,7 @@ static void *get_any_partial(struct kmem_cache *s, gfp_t flags,
do {
cpuset_mems_cookie = get_mems_allowed();
zonelist = node_zonelist(slab_node(current->mempolicy), flags);
zonelist = node_zonelist(slab_node(), flags);
for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
struct kmem_cache_node *n;