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([2601:188:c102:b180:1f8b:71d0:77b1:1f6e]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2b05ff8634csm69342683eec.3.2025.12.28.19.53.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 28 Dec 2025 19:53:54 -0800 (PST) From: Waiman Long X-Google-Original-From: Waiman Long Message-ID: <81f201cc-395a-48d7-a1b0-db8c62b93c9e@redhat.com> Date: Sun, 28 Dec 2025 22:53:41 -0500 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 01/33] PCI: Prepare to protect against concurrent isolated cpuset change To: Zhang Qiao , 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 , 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> <20251224134520.33231-2-frederic@kernel.org> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 12/28/25 10:23 PM, Zhang Qiao wrote: > Hi, Weisbecker， > > 在 2025/12/24 21:44, Frederic Weisbecker 写道: >> HK_TYPE_DOMAIN will soon integrate cpuset isolated partitions and >> therefore be made modifiable at runtime. Synchronize against the cpumask >> update using RCU. >> >> The RCU locked section includes both the housekeeping CPU target >> election for the PCI probe work and the work enqueue. >> >> This way the housekeeping update side will simply need to flush the >> pending related works after updating the housekeeping mask in order to >> make sure that no PCI work ever executes on an isolated CPU. This part >> will be handled in a subsequent patch. >> >> Signed-off-by: Frederic Weisbecker >> --- >> drivers/pci/pci-driver.c | 47 ++++++++++++++++++++++++++++++++-------- >> 1 file changed, 38 insertions(+), 9 deletions(-) >> >> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c >> index 7c2d9d596258..786d6ce40999 100644 >> --- a/drivers/pci/pci-driver.c >> +++ b/drivers/pci/pci-driver.c >> @@ -302,9 +302,8 @@ struct drv_dev_and_id { >> const struct pci_device_id *id; >> }; >> >> -static long local_pci_probe(void *_ddi) >> +static int local_pci_probe(struct drv_dev_and_id *ddi) >> { >> - struct drv_dev_and_id *ddi = _ddi; >> struct pci_dev *pci_dev = ddi->dev; >> struct pci_driver *pci_drv = ddi->drv; >> struct device *dev = &pci_dev->dev; >> @@ -338,6 +337,19 @@ static long local_pci_probe(void *_ddi) >> return 0; >> } >> >> +struct pci_probe_arg { >> + struct drv_dev_and_id *ddi; >> + struct work_struct work; >> + int ret; >> +}; >> + >> +static void local_pci_probe_callback(struct work_struct *work) >> +{ >> + struct pci_probe_arg *arg = container_of(work, struct pci_probe_arg, work); >> + >> + arg->ret = local_pci_probe(arg->ddi); >> +} >> + >> static bool pci_physfn_is_probed(struct pci_dev *dev) >> { >> #ifdef CONFIG_PCI_IOV >> @@ -362,34 +374,51 @@ static int pci_call_probe(struct pci_driver *drv, struct pci_dev *dev, >> dev->is_probed = 1; >> >> cpu_hotplug_disable(); >> - >> /* >> * Prevent nesting work_on_cpu() for the case where a Virtual Function >> * device is probed from work_on_cpu() of the Physical device. >> */ >> if (node < 0 || node >= MAX_NUMNODES || !node_online(node) || >> pci_physfn_is_probed(dev)) { >> - cpu = nr_cpu_ids; >> + error = local_pci_probe(&ddi); >> } else { >> cpumask_var_t wq_domain_mask; >> + struct pci_probe_arg arg = { .ddi = &ddi }; >> + >> + INIT_WORK_ONSTACK(&arg.work, local_pci_probe_callback); >> >> if (!zalloc_cpumask_var(&wq_domain_mask, GFP_KERNEL)) { >> error = -ENOMEM; > If we return from here, arg.work will not be destroyed. > > Right. INIT_WORK_ONSTACK() should be called after successful cpumask_var_t allocation. Cheers, Longman >> goto out; >> } >> + >> + /* >> + * The target election and the enqueue of the work must be within >> + * the same RCU read side section so that when the workqueue pool >> + * is flushed after a housekeeping cpumask update, further readers >> + * are guaranteed to queue the probing work to the appropriate >> + * targets. >> + */ >> + rcu_read_lock(); >> cpumask_and(wq_domain_mask, >> housekeeping_cpumask(HK_TYPE_WQ), >> housekeeping_cpumask(HK_TYPE_DOMAIN)); >> >> cpu = cpumask_any_and(cpumask_of_node(node), >> wq_domain_mask); >> + if (cpu < nr_cpu_ids) { >> + schedule_work_on(cpu, &arg.work); >> + rcu_read_unlock(); >> + flush_work(&arg.work); >> + error = arg.ret; >> + } else { >> + rcu_read_unlock(); >> + error = local_pci_probe(&ddi); >> + } >> + >> free_cpumask_var(wq_domain_mask); >> + destroy_work_on_stack(&arg.work); >> } >> - >> - if (cpu < nr_cpu_ids) >> - error = work_on_cpu(cpu, local_pci_probe, &ddi); >> - else >> - error = local_pci_probe(&ddi); >> out: >> dev->is_probed = 0; >> cpu_hotplug_enable(); >>