linux-kernel - [PATCH 06/27] mm: vmstat: Prepare to protect against concurrent isolated cpuset change

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Message-ID: <20250620152308.27492-7-frederic@kernel.org>
Date: Fri, 20 Jun 2025 17:22:47 +0200
From: Frederic Weisbecker <frederic@...nel.org>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Frederic Weisbecker <frederic@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Marco Crivellari <marco.crivellari@...e.com>,
	Michal Hocko <mhocko@...e.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Tejun Heo <tj@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Vlastimil Babka <vbabka@...e.cz>,
	Waiman Long <longman@...hat.com>,
	linux-mm@...ck.org
Subject: [PATCH 06/27] mm: vmstat: Prepare to protect against concurrent isolated cpuset change

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, read-lock the housekeeping rwsem lock while targeting
and queueing a vmstat work.

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 had been made isolated.

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

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 429ae5339bfe..53123675fe31 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -2115,11 +2115,13 @@ 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(housekeeping) {
+			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();
 	}
-- 
2.48.1