[PATCH 04/33] mm: vmstat: Prepare to protect against concurrent isolated cpuset change

Frederic Weisbecker
2025-10-13T20:32:29Z

The HK_TYPE_DOMAIN housekeeping cpumask will soon be made modifyable at
runtime. In order to synchronize against vmstat workqueue to make sure
that no asynchronous vmstat work is pending or executing on a newly made
isolated CPU, target and queue a vmstat work under the same RCU read
side critical section.

Whenever housekeeping will update the HK_TYPE_DOMAIN cpumask, a vmstat
workqueue flush will also be issued in a further change to make sure
that no work remains pending after a CPU has been made isolated.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
mm/vmstat.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index bb09c032eecf..7afb2981501f 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -2135,11 +2135,13 @@ static void vmstat_shepherd(struct work_struct *w)
* infrastructure ever noticing. Skip regular flushing from vmstat_shepherd
* for all isolated CPUs to avoid interference with the isolated workload.
*/
- if (cpu_is_isolated(cpu))
- continue;
+ scoped_guard(rcu) {
+ if (cpu_is_isolated(cpu))
+ continue;

- if (!delayed_work_pending(dw) && need_update(cpu))
- queue_delayed_work_on(cpu, mm_percpu_wq, dw, 0);
+ if (!delayed_work_pending(dw) && need_update(cpu))
+ queue_delayed_work_on(cpu, mm_percpu_wq, dw, 0);
+ }

cond_resched();
}
--
2.51.0