linux-kernel - Re: [PATCH 2/2] PCI: Add lockdep assertion in pci_stop_and_remove_bus

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Message-ID: <48360cde-81d9-4161-8c32-0029e193c685@linux.ibm.com>
Date: Wed, 24 Sep 2025 11:06:22 -0700
From: Farhan Ali <alifm@...ux.ibm.com>
To: Niklas Schnelle <schnelle@...ux.ibm.com>,
        Bjorn Helgaas <helgaas@...nel.org>, Lukas Wunner <lukas@...ner.de>
Cc: Keith Busch <kbusch@...nel.org>, Gerd Bayer <gbayer@...ux.ibm.com>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        Benjamin Block <bblock@...ux.ibm.com>,
        Halil Pasic <pasic@...ux.ibm.com>,
        Julian Ruess <julianr@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev
 <agordeev@...ux.ibm.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] PCI: Add lockdep assertion in
 pci_stop_and_remove_bus_device()


On 8/26/2025 1:52 AM, Niklas Schnelle wrote:
> Removing a PCI devices requires holding pci_rescan_remove_lock. Prompted
> by this being missed in sriov_disable() and going unnoticed since its
> inception add a lockdep assert so this doesn't get missed again in the
> future.
>
> Reviewed-by: Benjamin Block <bblock@...ux.ibm.com>
> Signed-off-by: Niklas Schnelle <schnelle@...ux.ibm.com>
> ---
>   drivers/pci/pci.h    | 2 ++
>   drivers/pci/probe.c  | 2 +-
>   drivers/pci/remove.c | 1 +
>   3 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 34f65d69662e9f61f0c489ec58de2ce17d21c0c6..1ad2e3ab147f3b2c42b3257e4f366fc5e424ede3 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -84,6 +84,8 @@ struct pcie_tlp_log;
>   extern const unsigned char pcie_link_speed[];
>   extern bool pci_early_dump;
>   
> +extern struct mutex pci_rescan_remove_lock;
> +
>   bool pcie_cap_has_lnkctl(const struct pci_dev *dev);
>   bool pcie_cap_has_lnkctl2(const struct pci_dev *dev);
>   bool pcie_cap_has_rtctl(const struct pci_dev *dev);
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index f41128f91ca76ab014ad669ae84a53032c7c6b6b..2b35bb39ab0366bbf86b43e721811575b9fbcefb 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -3469,7 +3469,7 @@ EXPORT_SYMBOL_GPL(pci_rescan_bus);
>    * pci_rescan_bus(), pci_rescan_bus_bridge_resize() and PCI device removal
>    * routines should always be executed under this mutex.
>    */
> -static DEFINE_MUTEX(pci_rescan_remove_lock);
> +DEFINE_MUTEX(pci_rescan_remove_lock);
>   
>   void pci_lock_rescan_remove(void)
>   {
> diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
> index 445afdfa6498edc88f1ef89df279af1419025495..0b9a609392cecba36a818bc496a0af64061c259a 100644
> --- a/drivers/pci/remove.c
> +++ b/drivers/pci/remove.c
> @@ -138,6 +138,7 @@ static void pci_remove_bus_device(struct pci_dev *dev)
>    */
>   void pci_stop_and_remove_bus_device(struct pci_dev *dev)
>   {
> +	lockdep_assert_held(&pci_rescan_remove_lock);
>   	pci_stop_bus_device(dev);
>   	pci_remove_bus_device(dev);
>   }

We also have the function pci_stop_and_remove_bus_device_locked() as 
Gerd mentioned, so is pci_stop_and_remove_bus_device meant to be called 
without the rescan_remove_lock held? This is a little confusing as we 
shouldn't be adding/removing from the bus without the lock AFAIU, but 
maybe I am missing something?

Thanks
Farhan