From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756711AbaIKNOT (ORCPT ); Thu, 11 Sep 2014 09:14:19 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:51526 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755384AbaIKMeE (ORCPT ); Thu, 11 Sep 2014 08:34:04 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "David Rientjes" , penberg@kernel.org, "Andi Kleen" , "David Mackey" , "KOSAKI Motohiro" , cl@linux.com, "Arun Sharma" Date: Thu, 11 Sep 2014 13:32:13 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 121/131] slab/mempolicy: always use local policy from interrupt context In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.249 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.63-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Andi Kleen commit e7b691b085fda913830e5280ae6f724b2a63c824 upstream. 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 Cc: penberg@kernel.org Cc: cl@linux.com Signed-off-by: Andi Kleen [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 Acked-by: Christoph Lameter Acked-by: KOSAKI Motohiro Signed-off-by: David Mackey Signed-off-by: Pekka Enberg Signed-off-by: Ben Hutchings --- include/linux/mempolicy.h | 2 +- mm/mempolicy.c | 8 +++++++- mm/slab.c | 4 ++-- mm/slub.c | 2 +- 4 files changed, 11 insertions(+), 5 deletions(-) --- a/include/linux/mempolicy.h +++ b/include/linux/mempolicy.h @@ -205,7 +205,7 @@ extern struct zonelist *huge_zonelist(st 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; --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -1601,8 +1601,14 @@ static unsigned interleave_nodes(struct * 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(); --- a/mm/slab.c +++ b/mm/slab.c @@ -3270,7 +3270,7 @@ static void *alternate_node_alloc(struct 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; @@ -3302,7 +3302,7 @@ static void *fallback_alloc(struct kmem_ retry_cpuset: cpuset_mems_cookie = get_mems_allowed(); - zonelist = node_zonelist(slab_node(current->mempolicy), flags); + zonelist = node_zonelist(slab_node(), flags); retry: /* --- a/mm/slub.c +++ b/mm/slub.c @@ -1608,7 +1608,7 @@ static struct page *get_any_partial(stru 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;