sched: Ensure 'sched_domains_numa_levels' is safe to use in other functions

We should temporarily reset 'sched_domains_numa_levels' to 0 after
it is reset to 'level' in sched_init_numa(). If it fails to allocate
memory for array sched_domains_numa_masks[][], the array will contain
less then 'level' members. This could be dangerous when we use it to
iterate array sched_domains_numa_masks[][] in other functions.

This patch set sched_domains_numa_levels to 0 before initializing
array sched_domains_numa_masks[][], and reset it to 'level' when
sched_domains_numa_masks[][] is fully initialized.

Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1348578751-16904-2-git-send-email-tangchen@cn.fujitsu.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c177472..f895fdd 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6122,6 +6122,17 @@ static void sched_init_numa(void)
         * numbers.
         */
 
+       /*
+        * Here, we should temporarily reset sched_domains_numa_levels to 0.
+        * If it fails to allocate memory for array sched_domains_numa_masks[][],
+        * the array will contain less then 'level' members. This could be
+        * dangerous when we use it to iterate array sched_domains_numa_masks[][]
+        * in other functions.
+        *
+        * We reset it to 'level' at the end of this function.
+        */
+       sched_domains_numa_levels = 0;
+
        sched_domains_numa_masks = kzalloc(sizeof(void *) * level, GFP_KERNEL);
        if (!sched_domains_numa_masks)
                return;
@@ -6176,6 +6187,8 @@ static void sched_init_numa(void)
        }
 
        sched_domain_topology = tl;
+
+       sched_domains_numa_levels = level;
 }
 #else
 static inline void sched_init_numa(void)