(struct sg_lb_stats).idle_cpus is of type 'unsigned int'.
(local->idle_cpus - busiest->idle_cpus) can underflow to UINT_MAX
for instance, and max_t(long, 0, UINT_MAX) will output UINT_MAX.
Use lsub_positive() instead of max_t().
Fixes: 16b0a7a1a0af ("sched/fair: Ensure tasks spreading in LLC during LB")
cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Pierre Gondois <pierre.gondois@xxxxxxx>
Reviewed-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
---
kernel/sched/fair.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 9057584ec06d..6d9124499f52 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -10775,8 +10775,8 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
* idle CPUs.
*/
env->migration_type = migrate_task;
- env->imbalance = max_t(long, 0,
- (local->idle_cpus - busiest->idle_cpus));
+ env->imbalance = local->idle_cpus;
+ lsub_positive(&env->imbalance, busiest->idle_cpus);
}
#ifdef CONFIG_NUMA
--
2.25.1
