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[109.81.26.156]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-435b1f74b15sm31194587f8f.35.2026.01.26.08.41.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Jan 2026 08:41:39 -0800 (PST) Date: Mon, 26 Jan 2026 17:41:38 +0100 From: Michal Hocko To: Frederic Weisbecker Cc: LKML , Michal =?iso-8859-1?Q?Koutn=FD?= , Andrew Morton , Bjorn Helgaas , Catalin Marinas , Chen Ridong , Danilo Krummrich , "David S . Miller" , Eric Dumazet , Gabriele Monaco , Greg Kroah-Hartman , Ingo Molnar , Jakub Kicinski , Jens Axboe , Johannes Weiner , Lai Jiangshan , Marco Crivellari , Muchun Song , Paolo Abeni , Peter Zijlstra , Phil Auld , "Rafael J . Wysocki" , Roman Gushchin , Shakeel Butt , Simon Horman , Tejun Heo , Thomas Gleixner , Vlastimil Babka , Waiman Long , Will Deacon , cgroups@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-block@vger.kernel.org, linux-mm@kvack.org, linux-pci@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH 03/33] memcg: Prepare to protect against concurrent isolated cpuset change Message-ID: References: <20260125224541.50226-1-frederic@kernel.org> <20260125224541.50226-4-frederic@kernel.org> 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-Disposition: inline In-Reply-To: <20260125224541.50226-4-frederic@kernel.org> On Sun 25-01-26 23:45:10, Frederic Weisbecker wrote: > The HK_TYPE_DOMAIN housekeeping cpumask will soon be made modifiable at > runtime. In order to synchronize against memcg workqueue to make sure > that no asynchronous draining is pending or executing on a newly made > isolated CPU, target and queue a drain work under the same RCU critical > section. > > Whenever housekeeping will update the HK_TYPE_DOMAIN cpumask, a memcg > 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 > --- > mm/memcontrol.c | 21 +++++++++++++++++---- > 1 file changed, 17 insertions(+), 4 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index be810c1fbfc3..2289a0299331 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2003,6 +2003,19 @@ static bool is_memcg_drain_needed(struct memcg_stock_pcp *stock, > return flush; > } > > +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)) > + schedule_work_on(cpu, work); Shouldn't this in the guarded rcu section? -- Michal Hocko SUSE Labs