From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
3.12-stable review patch. If anyone has any objections, please let me know.
===============
commit 42eb088ed246a5a817bb45a8b32fe234cf1c0f8b upstream.
Commit 37dc6b50cee9 ("sched: Remove unnecessary iteration over sched
domains to update nr_busy_cpus") forgot to clear 'sd_busy' under some
conditions leading to a possible NULL deref in set_cpu_sd_state_idle().
Reported-by: Anton Blanchard <anton@xxxxxxxxx>
Cc: Preeti U Murthy <preeti@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20131118113701.GF3866@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
kernel/sched/core.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 6135b7c6bcfe..bc2f26d03751 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5132,8 +5132,9 @@ static void update_top_cache_domain(int cpu)
if (sd) {
id = cpumask_first(sched_domain_span(sd));
size = cpumask_weight(sched_domain_span(sd));
- rcu_assign_pointer(per_cpu(sd_busy, cpu), sd->parent);
+ sd = sd->parent; /* sd_busy */
}
+ rcu_assign_pointer(per_cpu(sd_busy, cpu), sd);
rcu_assign_pointer(per_cpu(sd_llc, cpu), sd);
per_cpu(sd_llc_size, cpu) = size;
--
1.9.0
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