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

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Message-ID: <aVRUUXa6kJKHHQ_n@pavilion.home>
Date: Tue, 30 Dec 2025 23:38:09 +0100
From: Frederic Weisbecker <frederic@...nel.org>
To: Zhang Qiao <zhangqiao22@...wei.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
	Michal Koutný <mkoutny@...e.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Chen Ridong <chenridong@...wei.com>,
	Danilo Krummrich <dakr@...nel.org>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Gabriele Monaco <gmonaco@...hat.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ingo Molnar <mingo@...hat.com>, Jakub Kicinski <kuba@...nel.org>,
	Jens Axboe <axboe@...nel.dk>, Johannes Weiner <hannes@...xchg.org>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Marco Crivellari <marco.crivellari@...e.com>,
	Michal Hocko <mhocko@...e.com>, Muchun Song <muchun.song@...ux.dev>,
	Paolo Abeni <pabeni@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>, Phil Auld <pauld@...hat.com>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Shakeel Butt <shakeel.butt@...ux.dev>,
	Simon Horman <horms@...nel.org>, Tejun Heo <tj@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Vlastimil Babka <vbabka@...e.cz>, Waiman Long <longman@...hat.com>,
	Will Deacon <will@...nel.org>, cgroups@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-block@...r.kernel.org,
	linux-mm@...ck.org, linux-pci@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH 01/33] PCI: Prepare to protect against concurrent
 isolated cpuset change

Le Mon, Dec 29, 2025 at 11:23:56AM +0800, Zhang Qiao a écrit :
> 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@...nel.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.

Good catch! Thanks.

-- 
Frederic Weisbecker
SUSE Labs