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Wed, 31 Dec 2025 07:30:41 -0800 (PST) Message-ID: <4156bbde-754b-470e-9dfb-a1e45bee81fb@kernel.dk> Date: Wed, 31 Dec 2025 08:30:39 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 09/33] block: Protect against concurrent isolated cpuset change To: Frederic Weisbecker Cc: LKML , =?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 , 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: <20251224134520.33231-1-frederic@kernel.org> <20251224134520.33231-10-frederic@kernel.org> <0f65c4fe-8b10-403d-b5b6-ed33fc4eb69c@kernel.dk> Content-Language: en-US From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: C770F16000B X-Stat-Signature: mikj64shzme7dgpjms9n5ewnxjzaed48 X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1767195043-243005 X-HE-Meta: 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 a58U3B04 Sgci/YdPGCh0iprhGJgPmHBCRwYt3UE9K8eOqDSvlDpC7kLK+sy+gwzu6LHHIDfSATtZqQROt/mejModQM6D3GMbS264CN3QphzW0uohBdsrlnXEP1vGaJ0yW7PoPsg+WKRpwyWrSQjX5syC5iaAQOfd5T5hDm0tMPyWfbJssdjGFrhYcQj1fN+YpUxBCkKZzyuvuVWNt6L4HIYr+4atr5eEJVh1+OznCSUnMP0BOaCpl7wsF48AVyQKOV/xjnA0KKfq/TaG8FWdNLD5qbdcfwjHnwQHuoRqC+ceUe+NVyu1GFPFg1ea7PXWtGbICAlli944n9JPWufbLE2LkTL7Lpy/nOoxfi0spotTq8wwIMrN5mxolJiqxaold7c1fvxSaALDC3Zq4CW/jqlCjQ8DLNRH0pk2mfY6lDIai X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 12/31/25 7:02 AM, Frederic Weisbecker wrote: > Le Mon, Dec 29, 2025 at 05:37:29PM -0700, Jens Axboe a ?crit : >> On 12/24/25 6:44 AM, Frederic Weisbecker wrote: >>> The block subsystem prevents running the workqueue to isolated CPUs, >>> including those defined by cpuset isolated partitions. Since >>> HK_TYPE_DOMAIN will soon contain both and be subject to runtime >>> modifications, synchronize against housekeeping using the relevant lock. >>> >>> For full support of cpuset changes, the block subsystem may need to >>> propagate changes to isolated cpumask through the workqueue in the >>> future. >>> >>> Signed-off-by: Frederic Weisbecker >>> --- >>> block/blk-mq.c | 6 +++++- >>> 1 file changed, 5 insertions(+), 1 deletion(-) >>> >>> diff --git a/block/blk-mq.c b/block/blk-mq.c >>> index 1978eef95dca..0037af1216f3 100644 >>> --- a/block/blk-mq.c >>> +++ b/block/blk-mq.c >>> @@ -4257,12 +4257,16 @@ static void blk_mq_map_swqueue(struct request_queue *q) >>> >>> /* >>> * Rule out isolated CPUs from hctx->cpumask to avoid >>> - * running block kworker on isolated CPUs >>> + * running block kworker on isolated CPUs. >>> + * FIXME: cpuset should propagate further changes to isolated CPUs >>> + * here. >>> */ >>> + rcu_read_lock(); >>> for_each_cpu(cpu, hctx->cpumask) { >>> if (cpu_is_isolated(cpu)) >>> cpumask_clear_cpu(cpu, hctx->cpumask); >>> } >>> + rcu_read_unlock(); >> >> Want me to just take this one separately and get it out of your hair? >> Doesn't seem to have any dependencies. > > The patch could be applied alone but the rest of the patchset needs it, > otherwise it may dereference freed memory. So I fear it needs to stay > within the lot. > > I appreciate the offer though. But an ack would help, even if I must admit > this single patch (which doesn't change current behaviour) leaves a > bitter taste because complete handling of cpuset isolated partition change > will require more work. That's fine too: Acked-by: Jens Axboe > Speaking of, is there a way that I missed to define/overwrite the above > hctx->cpumask on runtime? Only spot where it's set/manipulated right now is as part of setting up the hctx <-> ctx queue mappings, when the queue is configured (or reconfigured). -- Jens Axboe