From nobody Sat Sep 26 22:55:57 2026 Received: from shelob.surriel.com (shelob.surriel.com [96.67.55.147]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9BE37391E76; Fri, 28 Aug 2026 13:46:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=96.67.55.147 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787924793; cv=none; b=Uu78/4LHJQYYHVWNERCBKbimDut+THj5voqx72y/zECwOAZQEl9OsTOA8swCDzdAJUvFIltcaVUaMq39rn+Zquu2Z2QGjDGQtUuOZ82A6lChNxobiv7vcoOioiHHzx2QOtZdRHx5dq192AmLt3z4BBi2LkSylqBr7L/SdS+2ves= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787924793; c=relaxed/simple; bh=/AUbOXLbCVCQjm0+YW4SW5lQPjQLIXY9ybWXRRosM6M=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=jQb/hK2gvnF3KlGcTHVOdqmY1qZGGwvuBGHcu7CwIPEx6/xl17k80lw264cMTc5Twvl417ykwwDVVUhXeKJJf+45IEv2ZlWzn/DXQHYLacaobik/yugv+E+c3YZ3kYzd7a+sLo+oumEw0dP7OBjzbShX/SlQNMd3mIhav989nf0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=surriel.com; spf=pass smtp.mailfrom=surriel.com; dkim=pass (2048-bit key) header.d=surriel.com header.i=@surriel.com header.b=NnZNH0/K; arc=none smtp.client-ip=96.67.55.147 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=surriel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=surriel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=surriel.com header.i=@surriel.com header.b="NnZNH0/K" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=surriel.com ; s=mail; h=Content-Transfer-Encoding:MIME-Version:References:In-Reply-To: Message-ID:Date:Subject:Cc:To:From:Sender:Reply-To:Content-Type:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID; bh=9TfgXIoukN/RPVFm1I+e7bggSQFoinJyk03xgumztOQ=; b=NnZNH0 /Kz1ZEAaFeSw5eQJXsW2aeU6YbzoXE+iOLimV0vZZtb1oVYNMYEUZCo8JMBjKpMZ5yH3S+fV7vcOO qKk461zeTFImkVEIeTIpUS67b/cbPvv3oafPXwDHdNEvexeCxV7yIC+3LB96cKgC5sPzpJRSvRdbh 010F/tSvQC0fN4cxlXGclzSXZr30Ef+qTdbZ8anTTk9OJG99VpeaZlkMMnKqTjBwdyzPVONjx6mDP Em0DOkkIWD5/vDbr5QmPWTt8vECuVzUT9VG1tCybO8bgQ4lmCMr3+GuPwOzV4reJwTTlSiEurXxNN xGPVYZIIcqD5gp6WYwvyp/Ai+onA==; Received: from [2601:18c:8100:a0e0:5a47:caff:fe78:8708] (helo=fangorn.surriel.com) by shelob.surriel.com with esmtpsa (TLS1.3) tls TLS_AES_256_GCM_SHA384 (Exim 4.99.5) (envelope-from ) id 1wzwuY-00000008zmT-0utG; Fri, 28 Aug 2026 13:46:26 +0000 From: Rik van Riel To: linux-kernel@vger.kernel.org Cc: Rik van Riel , Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , cgroups@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com, stable@vger.kernel.org Subject: [PATCH] mm/memcontrol: avoid stuck FLUSHING_CACHED_CHARGE bit on isolated cpus Date: Fri, 28 Aug 2026 09:46:21 -0400 Message-ID: X-Mailer: git-send-email 2.55.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" drain_all_stock() can leave FLUSHING_CACHED_CHARGE set after the work is dropped. It sets the bit before checking isolation and schedule_drain_work() checks isolation and queues in a separate RCU critical section, so housekeeping_update()'s synchronize_rcu() can race the second check. drain_local_stock() only clears the bit for work that ran, so the bit remains set and the stock is never drained again. Reorganize the drain_all_stock() loop, reducing nesting, splitting out local vs remote cpu handling, and skipping everything on isolated cpus, which solves the stuck FLUSHING_CACHED_CHARGE flag. Fixes: 6a792697a53a ("memcg: do not drain charge pcp caches on remote isola= ted cpus") Cc: stable@vger.kernel.org Assisted-by: Hermes:muse-spark-1.2 Signed-off-by: Rik van Riel diff --git a/mm/memcontrol.c b/mm/memcontrol.c index a660ea0f820b..b0d8ec042d48 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2330,19 +2330,6 @@ static bool obj_stock_should_drain(struct obj_stock_= pcp *stock, return true; } =20 -static void schedule_drain_work(int cpu, struct work_struct *work) -{ - /* - * Protect housekeeping cpumask read and work enqueue together - * in the same RCU critical section so that later cpuset isolated - * partition update only need to wait for an RCU GP and flush the - * pending work on newly isolated CPUs. - */ - guard(rcu)(); - if (!cpu_is_isolated(cpu)) - queue_work_on(cpu, memcg_wq, work); -} - /* * Drains all per-CPU charge caches for given root_memcg resp. subtree * of the hierarchy under it. @@ -2366,19 +2353,23 @@ void drain_all_stock(struct mem_cgroup *root_memcg) struct memcg_stock_pcp *memcg_st =3D &per_cpu(memcg_stock, cpu); struct obj_stock_pcp *obj_st =3D &per_cpu(obj_stock, cpu); =20 - if (memcg_stock_should_drain(memcg_st, root_memcg)) { - if (cpu =3D=3D curcpu) + if (cpu =3D=3D curcpu) { + if (memcg_stock_should_drain(memcg_st, root_memcg)) drain_local_memcg_stock(&memcg_st->work); - else - schedule_drain_work(cpu, &memcg_st->work); - } - - if (obj_stock_should_drain(obj_st, root_memcg)) { - if (cpu =3D=3D curcpu) + if (obj_stock_should_drain(obj_st, root_memcg)) drain_local_obj_stock(&obj_st->work); - else - schedule_drain_work(cpu, &obj_st->work); + continue; } + + /* Pairs with RCU barrier in housekeeping_update(). */ + guard(rcu)(); + if (cpu_is_isolated(cpu)) + continue; + + if (memcg_stock_should_drain(memcg_st, root_memcg)) + queue_work_on(cpu, memcg_wq, &memcg_st->work); + if (obj_stock_should_drain(obj_st, root_memcg)) + queue_work_on(cpu, memcg_wq, &obj_st->work); } migrate_enable(); mutex_unlock(&percpu_charge_mutex);