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([2600:8803:e7e4:500:e37:2309:3937:4469]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-7d55b9a8498sm1062950a34.28.2026.02.23.08.01.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 23 Feb 2026 08:01:05 -0800 (PST) Message-ID: <47be2ff3-c25a-4aab-89fc-53921af8b0a9@baylibre.com> Date: Mon, 23 Feb 2026 10:01:03 -0600 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 04/33] mm: vmstat: Prepare to protect against concurrent isolated cpuset change To: Frederic Weisbecker , LKML Cc: =?UTF-8?Q?Michal_Koutn=C3=BD?= , 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 , Michal Hocko , 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 References: <20260101221359.22298-1-frederic@kernel.org> <20260101221359.22298-5-frederic@kernel.org> Content-Language: en-US From: David Lechner In-Reply-To: <20260101221359.22298-5-frederic@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/1/26 4:13 PM, Frederic Weisbecker wrote: > The HK_TYPE_DOMAIN housekeeping cpumask will soon be made modifiable 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 > --- > mm/vmstat.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/mm/vmstat.c b/mm/vmstat.c > index 65de88cdf40e..ed19c0d42de6 100644 > --- a/mm/vmstat.c > +++ b/mm/vmstat.c > @@ -2144,11 +2144,13 @@ 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; I think this might have introduced a bug - or at least an unintentional change in the program flow. scoped_guard() is implemented using a for loop. Now this continue statement will only exit the scoped_guard() scope rather than continuing the outer for loop. This means that cond_resched() will be called when it previously was not. > > - 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(); > }