linux-kernel - Re: [PATCH 23/33] PCI: Remove superfluous HK_TYPE

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Message-ID: <20260122161505.GA1250310@bhelgaas>
Date: Thu, 22 Jan 2026 10:15:05 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Frederic Weisbecker <frederic@...nel.org>
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 23/33] PCI: Remove superfluous HK_TYPE_WQ check

On Thu, Jan 01, 2026 at 11:13:48PM +0100, Frederic Weisbecker wrote:
> It doesn't make sense to use nohz_full without also isolating the
> related CPUs from the domain topology, either through the use of
> isolcpus= or cpuset isolated partitions.
> 
> And now HK_TYPE_DOMAIN includes all kinds of domain isolated CPUs.
> 
> This means that HK_TYPE_KERNEL_NOISE (of which HK_TYPE_WQ is only an
> alias) should always be a subset of HK_TYPE_DOMAIN.
> 
> Therefore sane configurations verify:
> 
> 	HK_TYPE_KERNEL_NOISE | HK_TYPE_DOMAIN == HK_TYPE_DOMAIN
> 
> Simplify the PCI probe target election accordingly.
> 
> Signed-off-by: Frederic Weisbecker <frederic@...nel.org>

Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>

> ---
>  drivers/pci/pci-driver.c | 17 +++--------------
>  1 file changed, 3 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> index b902d8adf9a5..a9590601835a 100644
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -384,16 +384,9 @@ static int pci_call_probe(struct pci_driver *drv, struct pci_dev *dev,
>  	    pci_physfn_is_probed(dev)) {
>  		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
> @@ -402,12 +395,9 @@ static int pci_call_probe(struct pci_driver *drv, struct pci_dev *dev,
>  		 * 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);
> +				      housekeeping_cpumask(HK_TYPE_DOMAIN));
> +
>  		if (cpu < nr_cpu_ids) {
>  			struct workqueue_struct *wq = pci_probe_wq;
>  
> @@ -422,10 +412,9 @@ static int pci_call_probe(struct pci_driver *drv, struct pci_dev *dev,
>  			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();
>  	return error;
> -- 
> 2.51.1
>