linux-kernel - Re: [PATCH v3] PCI: pci_call_probe: call local_pci

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Message-ID: <a50b3865-8a04-4a9a-8d27-b317619a75c0@linux.intel.com>
Date: Mon, 22 Jul 2024 15:39:39 +0800
From: Ethan Zhao <haifeng.zhao@...ux.intel.com>
To: Hongchen Zhang <zhanghongchen@...ngson.cn>,
 Markus Elfring <Markus.Elfring@....de>, Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Alex Belits <abelits@...vell.com>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Nitesh Narayan Lal <nitesh@...hat.com>,
 Frederic Weisbecker <frederic@...nel.org>, linux-pci@...r.kernel.org,
 linux-kernel@...r.kernel.org, loongarch@...ts.linux.dev,
 stable@...r.kernel.org, Huacai Chen <chenhuacai@...ngson.cn>
Subject: Re: [PATCH v3] PCI: pci_call_probe: call local_pci_probe() when
 selected cpu is offline


On 6/13/2024 3:42 PM, Hongchen Zhang wrote:
> Call work_on_cpu(cpu, fn, arg) in pci_call_probe() while the argument
> @cpu is a offline cpu would cause system stuck forever.
>
> This can be happen if a node is online while all its CPUs are
> offline (We can use "maxcpus=1" without "nr_cpus=1" to reproduce it).
>
> So, in the above case, let pci_call_probe() call local_pci_probe()
> instead of work_on_cpu() when the best selected cpu is offline.
>
> Fixes: 69a18b18699b ("PCI: Restrict probe functions to housekeeping CPUs")
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
> Signed-off-by: Hongchen Zhang <zhanghongchen@...ngson.cn>
> ---
> v2 -> v3: Modify commit message according to Markus's suggestion
> v1 -> v2: Add a method to reproduce the problem
> ---
>   drivers/pci/pci-driver.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> index af2996d0d17f..32a99828e6a3 100644
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -386,7 +386,7 @@ static int pci_call_probe(struct pci_driver *drv, struct pci_dev *dev,
>   		free_cpumask_var(wq_domain_mask);
>   	}
>   
> -	if (cpu < nr_cpu_ids)

Why not choose the right cpu to callwork_on_cpu() ? the one that is online. Thanks, Ethan

> +	if ((cpu < nr_cpu_ids) && cpu_online(cpu))
>   		error = work_on_cpu(cpu, local_pci_probe, &ddi);
>   	else
>   		error = local_pci_probe(&ddi);