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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 Subject: Re: [PATCH 09/33] block: Protect against concurrent isolated cpuset change Message-ID: References: <20251224134520.33231-1-frederic@kernel.org> <20251224134520.33231-10-frederic@kernel.org> <0f65c4fe-8b10-403d-b5b6-ed33fc4eb69c@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <0f65c4fe-8b10-403d-b5b6-ed33fc4eb69c@kernel.dk> X-Rspam-User: X-Rspamd-Queue-Id: 7FCCF8000B X-Rspamd-Server: rspam10 X-Stat-Signature: h5z5k6sfxybici1k7f8zpjfezk5pagtm X-HE-Tag: 1767189758-105186 X-HE-Meta: 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 qIXfx3Cu FIH93CmN9mOpGf5cz0/BvLkMrC6nKHqQmJV9sU5AknFhl2u4rxyXMWtxU58J0V1iyIrM6wIBRFjEcEHcS8y2YWi/X/vCioDw9BQfGimHVhS3FBNjWwPCpJz7kEaj1q0C0grBuSF2/+X4wuXc/+lUjeJC/HUGDr+AFsMI2c16u1ofYSg+Q5LFFJMpZSTap2dLEIqOuM9q2DakDSss6bYsBTV87eKIcfMM/O2M/PjWoGOO5RUkGo8zOfVEDdqHeMWSuUYg9 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: Le Mon, Dec 29, 2025 at 05:37:29PM -0700, Jens Axboe a écrit : > 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. Speaking of, is there a way that I missed to define/overwrite the above hctx->cpumask on runtime? Thanks. -- Frederic Weisbecker SUSE Labs