[tip: sched/core] sched/fair: Reset NUMA fault locality after scan period update

[tip-bot2 for Eric Kim]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     e81ee06308379a5f2ededf997bcf17551bce5db7
Gitweb:        https://git.kernel.org/tip/e81ee06308379a5f2ededf997bcf17551bce5db7
Author:        Eric Kim <seohyun.kim@xxxxxxxxxx>
AuthorDate:    Tue, 18 Aug 2026 12:48:29 +09:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Thu, 10 Sep 2026 11:01:30 +02:00

sched/fair: Reset NUMA fault locality after scan period update

When updating the task scan period for NUMA locality checks,
update_task_scan_period() checks whether there were no faults or failed
migration on the last scan window, at which it prolongs the scan period.

However, p->numa_faults_locality, which is used to check for migration
failure and number of faults at the previous scan window is not cleared
after changing the scan period, which unintentionally increases
numa_scan_period up to numa_scan_period_max even when there were no
migration failures or no faults at previous scan.

Fix this by jumping to the out label on early exit at this case to
ensure p->numa_faults_locality is always cleared before returning.

Closes: https://lore.kernel.org/all/20250404095354.311156-1-qlsdnjs236@xxxxxxxxxxxxxx/
Reported-by: Binwon Song <qlsdnjs236@xxxxxxxxxxxxxx>
Signed-off-by: Eric Kim <seohyun.kim@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://patch.msgid.link/Message-ID:
---
 kernel/sched/fair.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b8bd308..a42360c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3514,7 +3514,7 @@ static void update_task_scan_period(struct task_struct *p,
 		p->mm->numa_next_scan = jiffies +
 			msecs_to_jiffies(p->numa_scan_period);
 
-		return;
+		goto out;
 	}
 
 	/*
@@ -3558,7 +3558,10 @@ static void update_task_scan_period(struct task_struct *p,
 
 	p->numa_scan_period = clamp(p->numa_scan_period + diff,
 			task_scan_min(p), task_scan_max(p));
-	memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
+
+out:
+	memset(p->numa_faults_locality, 0,
+	       sizeof(p->numa_faults_locality));
 }
 
 /*