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Subject[GIT PULL] scheduler fix
Linus,

Please pull the latest sched-urgent-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched-urgent-for-linus

# HEAD: 9cfb38a7ba5a9c27c1af8093fb1af4b699c0a441 sched/fair: Fix sched domains NULL dereference in select_idle_sibling()

Fix a crash that can trigger when racing with CPU hotplug: we didn't use
sched-domains data structures carefully enough in select_idle_cpu().

Thanks,

Ingo

------------------>
Wanpeng Li (1):
sched/fair: Fix sched domains NULL dereference in select_idle_sibling()


kernel/sched/fair.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 502e95a6e927..8b03fb5d1b9e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5471,13 +5471,18 @@ static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd
*/
static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target)
{
- struct sched_domain *this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
- u64 avg_idle = this_rq()->avg_idle;
- u64 avg_cost = this_sd->avg_scan_cost;
+ struct sched_domain *this_sd;
+ u64 avg_cost, avg_idle = this_rq()->avg_idle;
u64 time, cost;
s64 delta;
int cpu, wrap;

+ this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
+ if (!this_sd)
+ return -1;
+
+ avg_cost = this_sd->avg_scan_cost;
+
/*
* Due to large variance we need a large fuzz factor; hackbench in
* particularly is sensitive here.
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