linux-kernel - Re: [PATCH] PCI: use local_pci_probe when best selected cpu is offline

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Date: Tue, 4 Jun 2024 22:57:06 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Hongchen Zhang <zhanghongchen@...ngson.cn>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>, Huacai Chen <chenhuacai@...ngson.cn>, 
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org, 
	loongarch@...ts.linux.dev, stable@...r.kernel.org
Subject: Re: [PATCH] PCI: use local_pci_probe when best selected cpu is offline

Hi, Hongchen,

On Wed, May 29, 2024 at 7:19 PM Hongchen Zhang
<zhanghongchen@...ngson.cn> wrote:
The title should be better like this:
PCI: Use local_pci_probe() when best selected CPU is offline

>
> When the best selected cpu is offline, work_on_cpu will stuck
> forever. Therefore, in this case, we should call
> local_pci_probe instead of work_on_cpu.

It is better to reword like this:

When the best selected CPU is offline, work_on_cpu() will 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), Therefore,
in this case, we should call local_pci_probe() instead of work_on_cpu().

Huacai

>
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
> Signed-off-by: Hongchen Zhang <zhanghongchen@...ngson.cn>
> ---
>  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)
> +       if ((cpu < nr_cpu_ids) && cpu_online(cpu))
>                 error = work_on_cpu(cpu, local_pci_probe, &ddi);
>         else
>                 error = local_pci_probe(&ddi);
> --
> 2.33.0
>
>