[tip:sched/urgent] sched: Fix crash in sched_init_numa()

[tip-bot for Raghavendra K T]

Commit-ID:  9c03ee147193645be4c186d3688232fa438c57c7
Gitweb:     http://git.kernel.org/tip/9c03ee147193645be4c186d3688232fa438c57c7
Author:     Raghavendra K T <raghavendra.kt at linux.vnet.ibm.com>
AuthorDate: Sat, 16 Jan 2016 00:31:23 +0530
Committer:  Ingo Molnar <mingo at kernel.org>
CommitDate: Tue, 19 Jan 2016 08:42:20 +0100

sched: Fix crash in sched_init_numa()

The following PowerPC commit:

  c118baf80256 ("arch/powerpc/mm/numa.c: do not allocate bootmem memory for non existing nodes")

avoids allocating bootmem memory for non existent nodes.

But when DEBUG_PER_CPU_MAPS=y is enabled, my powerNV system failed to boot
because in sched_init_numa(), cpumask_or() operation was done on
unallocated nodes.

Fix that by making cpumask_or() operation only on existing nodes.

[ Tested with and w/o DEBUG_PER_CPU_MAPS=y on x86 and PowerPC. ]

Reported-by: Jan Stancek <jstancek at redhat.com>
Tested-by: Jan Stancek <jstancek at redhat.com>
Signed-off-by: Raghavendra K T <raghavendra.kt at linux.vnet.ibm.com>
Cc: <gkurz at linux.vnet.ibm.com>
Cc: <grant.likely at linaro.org>
Cc: <nikunj at linux.vnet.ibm.com>
Cc: <vdavydov at parallels.com>
Cc: <linuxppc-dev at lists.ozlabs.org>
Cc: <linux-mm at kvack.org>
Cc: <peterz at infradead.org>
Cc: <benh at kernel.crashing.org>
Cc: <paulus at samba.org>
Cc: <mpe at ellerman.id.au>
Cc: <anton at samba.org>
Link: http://lkml.kernel.org/r/1452884483-11676-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo at kernel.org>
---
 kernel/sched/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 44253ad..474658b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6840,7 +6840,7 @@ static void sched_init_numa(void)
 
 			sched_domains_numa_masks[i][j] = mask;
 
-			for (k = 0; k < nr_node_ids; k++) {
+			for_each_node(k) {
 				if (node_distance(j, k) > sched_domains_numa_distance[i])
 					continue;