Re: [PATCH v13 1/2] PCI/IOV: Make pci_lock_rescan_remove() reentrant and protect sriov_add_vfs/sriov_del_vfs

[Benjamin Block]

On Tue, Apr 21, 2026 at 10:34:20AM +0300, Ionut Nechita (Wind River) wrote:
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index b63cd0c310bc..0e62081bc5e5 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -3513,16 +3513,30 @@ EXPORT_SYMBOL_GPL(pci_rescan_bus);
>   * routines should always be executed under this mutex.
>   */
>  DEFINE_MUTEX(pci_rescan_remove_lock);
> +static struct task_struct *pci_rescan_remove_owner;

You could make this variable `const`:

    static const struct task_struct *pci_rescan_remove_owner;

so it is clear that this pointer is not meant to be used to modify the
task_struct in any way - just for these comparisons.

> +static unsigned int pci_rescan_remove_depth;
>  
>  void pci_lock_rescan_remove(void)
>  {
> -	mutex_lock(&pci_rescan_remove_lock);
> +	if (pci_rescan_remove_owner == current) {
> +		pci_rescan_remove_depth++;
> +	} else {
> +		mutex_lock(&pci_rescan_remove_lock);
> +		pci_rescan_remove_owner = current;
> +		pci_rescan_remove_depth = 1;
> +	}
>  }
>  EXPORT_SYMBOL_GPL(pci_lock_rescan_remove);
>  
>  void pci_unlock_rescan_remove(void)
>  {
> -	mutex_unlock(&pci_rescan_remove_lock);
> +	if (WARN_ON(pci_rescan_remove_owner != current))
> +		return;
> +
> +	if (--pci_rescan_remove_depth == 0) {
> +		pci_rescan_remove_owner = NULL;
> +		mutex_unlock(&pci_rescan_remove_lock);
> +	}
>  }
>  EXPORT_SYMBOL_GPL(pci_unlock_rescan_remove);


But anyway, with, or without this change, this looks good to me. I hadn't run
into any linker issues, but I only ever used our debug config.
Also holds up with my tests on my s390 rig.


Reviewed-by: Benjamin Block <bblock@xxxxxxxxxxxxx>
Tested-by: Benjamin Block <bblock@xxxxxxxxxxxxx>


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