[PATCH 1/6] sched/numa: clear fault locality state on execve

[Li Zhe]

task_numa_free(p, false) is used by execve() to reset NUMA balancing
state without freeing p->numa_faults, because concurrent readers may
still observe the task.

The non-final path clears p->total_numa_faults and the averaged half of
the retained p->numa_faults array, but leaves the current-window buffer
half and p->numa_faults_locality unchanged. Those are also NUMA fault
feedback consumed by task_numa_placement() and update_task_scan_period(),
so a newly executed image can inherit stale fault feedback from the old
image.

Clear the whole retained p->numa_faults array and p->numa_faults_locality
together in the non-final reset path.

Fixes: 04bb2f947505 ("sched/numa: Adjust scan rate in task_numa_placement")
Signed-off-by: Li Zhe <lizhe.67@xxxxxxxxxxxxx>
---
 kernel/sched/fair.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 57360f5cdde4..1053437933ee 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4177,8 +4177,9 @@ void task_numa_free(struct task_struct *p, bool final)
 		kfree(numa_faults);
 	} else {
 		p->total_numa_faults = 0;
-		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
-			numa_faults[i] = 0;
+		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
+		memset(numa_faults, 0, sizeof(*numa_faults) *
+		       NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids);
 	}
 }
 
-- 
2.20.1