From mboxrd@z Thu Jan 1 00:00:00 1970 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 22714364058; Fri, 28 Aug 2026 17:50:46 +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=1787939448; cv=none; b=t6520VGYq35QTtgBzC7m9Jnwe3NInYcou2sxtHrfbdGsAL6bEYCGen7myZZXScZx90Gqo17fKUudkvqrrvuXSnHADywMlEkt1Q06bM36n6Q+PKon3+UCz3MH6Cn0mhCfVmkPFkzMBP7Ul+z9igSjFq02GzGtDa/aAMpDJx1rlbw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787939448; c=relaxed/simple; bh=JvJ+o6146P4oRHKDVyAsH1RN98XuBcxixGMSU5PVFZc=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type; b=nlaAVQA6rta1Um+xSleeJOlhoV74/tjG3QiEfc/pn0ky1V0vhOY0xGvqwXha5FFv3fKm2fd3lBXU2e5caAgMvoQfl/DznMt49olqnkJVOVXqWmJBE/7w98m/t03JSLgUhbn9Grfa3TcNrq+vum/OvGTpt88mO3z/gn8VlTxvg9c= 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=hzwq2uTi; 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="hzwq2uTi" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=surriel.com ; s=mail; h=Content-Transfer-Encoding:Content-Type:MIME-Version:Message-ID: Subject:Cc:To:From:Date:Sender:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: In-Reply-To:References; bh=HRZSERTM0W44dOUuuxbU9VU3oVx0AWLYRmfUpfpxEzc=; b=hz wq2uTiBTs8IkwanKDfjgJVs1pnY2pp2w3uzTcO7HgW8d1Hvy8ZeNbPuQ1SxbBooaq/QUzSrOHiEpb 7TQD2iTEBnTiB5qScFe5IN6zrGaNINE4x7Q1uv1k9OOr+Z0zhRQcUnP81v+8Mv/7ukzZYYpLDumoX ENifvuszFTj8zU5VW+5QRvMWO0Qv5oDaSEBrPqru6G8G5DVTbHnIWfox7sOJTlmHwXCx2iXrYkU1E GDP44K8sM89Eueh9TO2HSnS+0JVnmrlSf6N3N9WgA7onuMh2BfLA3nya5z6wXkJ8DlMtFo8KxS5rM vaQlQ8hR5eHXWUSKVMy7/0Wvvbw/aORw==; Received: from [2601:18c:8100:a0e0:5a47:caff:fe78:8708] (helo=fangorn) by shelob.surriel.com with esmtpsa (TLS1.3) tls TLS_AES_256_GCM_SHA384 (Exim 4.99.5) (envelope-from ) id 1x00ir-000000093Tk-0mpH; Fri, 28 Aug 2026 17:50:37 +0000 Date: Fri, 28 Aug 2026 13:50:36 -0400 From: Rik van Riel To: linux-kernel@vger.kernel.org Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , cgroups@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com Subject: [PATCH v2] mm/memcontrol: fix stuck FLUSHING_CACHED_CHARGE bit on isolated cpus Message-ID: <20260828135036.7d44361f@fangorn> X-Mailer: Claws Mail 4.4.0 (GTK 3.24.52; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit When drain_all_stock() sets FLUSHING_CACHED_CHARGE before checking isolation, schedule_drain_work() can drop the work in a separate RCU critical section, and housekeeping_update()'s synchronize_rcu() can race that second check, leaving the flag set. drain_local_stock() only clears the bit for work that ran, so the flag remains set and the stock is never drained again. Have schedule_drain_work() return whether the work was queued, and clear FLUSHING_CACHED_CHARGE in drain_all_stock() when the remote CPU is isolated, so future drains can retry. Fixes: 6a792697a53a ("memcg: do not drain charge pcp caches on remote isolated cpus") Cc: stable@vger.kernel.org Suggested-by: Michal Hocko Suggested-by: Shakeel Butt Signed-off-by: Rik van Riel --- v2: use the approach suggested by Michal and Shakeel Link: https://lore.kernel.org/all/cover.1787890328.git.riel@surriel.com/ mm/memcontrol.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 1271d390b617..309398e943ca 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2306,7 +2306,7 @@ static bool is_memcg_drain_needed(struct memcg_stock_pcp *stock, return flush; } -static void schedule_drain_work(int cpu, struct work_struct *work) +static bool schedule_drain_work(int cpu, struct work_struct *work) { /* * Protect housekeeping cpumask read and work enqueue together @@ -2315,8 +2315,11 @@ static void schedule_drain_work(int cpu, struct work_struct *work) * pending work on newly isolated CPUs. */ guard(rcu)(); - if (!cpu_is_isolated(cpu)) - queue_work_on(cpu, memcg_wq, work); + if (cpu_is_isolated(cpu)) + return false; + + queue_work_on(cpu, memcg_wq, work); + return true; } /* @@ -2348,8 +2351,9 @@ void drain_all_stock(struct mem_cgroup *root_memcg) &memcg_st->flags)) { if (cpu == curcpu) drain_local_memcg_stock(&memcg_st->work); - else - schedule_drain_work(cpu, &memcg_st->work); + else if (!schedule_drain_work(cpu, &memcg_st->work)) + clear_bit(FLUSHING_CACHED_CHARGE, + &memcg_st->flags); } if (!test_bit(FLUSHING_CACHED_CHARGE, &obj_st->flags) && @@ -2358,8 +2362,9 @@ void drain_all_stock(struct mem_cgroup *root_memcg) &obj_st->flags)) { if (cpu == curcpu) drain_local_obj_stock(&obj_st->work); - else - schedule_drain_work(cpu, &obj_st->work); + else if (!schedule_drain_work(cpu, &obj_st->work)) + clear_bit(FLUSHING_CACHED_CHARGE, + &obj_st->flags); } } migrate_enable(); -- 2.55.0