Commit 608fedd2 authored by Frederic Weisbecker's avatar Frederic Weisbecker
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PCI: Prepare to protect against concurrent isolated cpuset change 



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: default avatarFrederic Weisbecker <frederic@kernel.org>
Acked-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Cc: linux-pci@vger.kernel.org
Cc: Marco Crivellari <marco.crivellari@suse.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Waiman Long <longman@redhat.com>
parent 9448598b

drivers/pci/pci-driver.c

+38 −9
Original line number Diff line number Diff line
@@ -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 };



		if (!zalloc_cpumask_var(&wq_domain_mask, GFP_KERNEL)) {

			error = -ENOMEM;

			goto out;

		}



		INIT_WORK_ONSTACK(&arg.work, local_pci_probe_callback);



		/*

		 * 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);

		free_cpumask_var(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);

		}



	if (cpu < nr_cpu_ids)

		error = work_on_cpu(cpu, local_pci_probe, &ddi);

	else

		error = local_pci_probe(&ddi);

		free_cpumask_var(wq_domain_mask);

		destroy_work_on_stack(&arg.work);

	}

out:

	dev->is_probed = 0;

	cpu_hotplug_enable();