[PATCH 15/33] sched/isolation: Flush vmstat workqueues on cpuset isolated partition change

Frederic Weisbecker
2025-10-13T20:33:57Z

The HK_TYPE_DOMAIN housekeeping cpumask is now modifyable at runtime.
In order to synchronize against vmstat workqueue to make sure
that no asynchronous vmstat work is still pending or executing on a
newly made isolated CPU, the housekeeping susbsystem must flush the
vmstat workqueues.

This involves flushing the whole mm_percpu_wq workqueue, shared with
LRU drain, introducing here a welcome side effect.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
include/linux/vmstat.h | 2 ++
kernel/sched/isolation.c | 1 +
kernel/sched/sched.h | 1 +
mm/vmstat.c | 5 +++++
4 files changed, 9 insertions(+)

diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index c287998908bf..a81aa5635b47 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -303,6 +303,7 @@ int calculate_pressure_threshold(struct zone *zone);
int calculate_normal_threshold(struct zone *zone);
void set_pgdat_percpu_threshold(pg_data_t *pgdat,
int (*calculate_pressure)(struct zone *));
+void vmstat_flush_workqueue(void);
#else /* CONFIG_SMP */

/*
@@ -403,6 +404,7 @@ static inline void __dec_node_page_state(struct page *page,
static inline void refresh_zone_stat_thresholds(void) { }
static inline void cpu_vm_stats_fold(int cpu) { }
static inline void quiet_vmstat(void) { }
+static inline void vmstat_flush_workqueue(void) { }

static inline void drain_zonestat(struct zone *zone,
struct per_cpu_zonestat *pzstats) { }
diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index 9ec365dea921..5cd3d98a2663 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -145,6 +145,7 @@ int housekeeping_update(struct cpumask *mask, enum hk_type type)
synchronize_rcu();

mem_cgroup_flush_workqueue();
+ vmstat_flush_workqueue();

kfree(old);

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 8bfc0b4b133f..84525885a3de 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -68,6 +68,7 @@
#include <linux/types.h>
#include <linux/u64_stats_sync_api.h>
#include <linux/uaccess.h>
+#include <linux/vmstat.h>
#include <linux/wait_api.h>
#include <linux/wait_bit.h>
#include <linux/workqueue_api.h>
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 7afb2981501f..506d3ca2e47f 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -2115,6 +2115,11 @@ static void vmstat_shepherd(struct work_struct *w);

static DECLARE_DEFERRABLE_WORK(shepherd, vmstat_shepherd);

+void vmstat_flush_workqueue(void)
+{
+ flush_workqueue(mm_percpu_wq);
+}
+
static void vmstat_shepherd(struct work_struct *w)
{
int cpu;
--
2.51.0