Re: [PATCH 01/33] PCI: Prepare to protect against concurrent isolated cpuset change

[Zhang Qiao <zhangqiao22@huawei.com>]

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 <frederic@kernel.org>
> ---
>  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.



>  			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();
>