From: Dexuan Cui <decui@xxxxxxxxxxxxx> Sent: Monday, April 3, 2023 7:06 PM
>
> Commit 414428c5da1c ("PCI: hv: Lock PCI bus on device eject") added
> pci_lock_rescan_remove() and pci_unlock_rescan_remove() in
> create_root_hv_pci_bus() and in hv_eject_device_work() to address the
> race between create_root_hv_pci_bus() and hv_eject_device_work(), but it
> turns that grubing the pci_rescan_remove_lock mutex is not enough:
> refer to the earlier fix "PCI: hv: Add a per-bus mutex state_lock".
>
> Now with hbus->state_lock and other fixes, the race is resolved, so
> remove pci_{lock,unlock}_rescan_remove() in create_root_hv_pci_bus():
> this removes the serialization in hv_pci_probe() and hence allows
> async-probing (PROBE_PREFER_ASYNCHRONOUS) to work.
>
> Add the async-probing flag to hv_pci_drv.
>
> pci_{lock,unlock}_rescan_remove() in hv_eject_device_work() and in
> hv_pci_remove() are still kept: according to the comment before
> drivers/pci/probe.c: static DEFINE_MUTEX(pci_rescan_remove_lock),
> "PCI device removal routines should always be executed under this mutex".
>
> Signed-off-by: Dexuan Cui <decui@xxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
>
> v2:
> No change to the patch body.
> Improved the commit message [Michael Kelley]
> Added Cc:stable
>
> drivers/pci/controller/pci-hyperv.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> index 3ae2f99dea8c2..2ea2b1b8a4c9a 100644
> --- a/drivers/pci/controller/pci-hyperv.c
> +++ b/drivers/pci/controller/pci-hyperv.c
> @@ -2312,12 +2312,16 @@ static int create_root_hv_pci_bus(struct
> hv_pcibus_device *hbus)
> if (error)
> return error;
>
> - pci_lock_rescan_remove();
> + /*
> + * pci_lock_rescan_remove() and pci_unlock_rescan_remove() are
> + * unnecessary here, because we hold the hbus->state_lock, meaning
> + * hv_eject_device_work() and pci_devices_present_work() can't race
> + * with create_root_hv_pci_bus().
> + */
> hv_pci_assign_numa_node(hbus);
> pci_bus_assign_resources(bridge->bus);
> hv_pci_assign_slots(hbus);
> pci_bus_add_devices(bridge->bus);
> - pci_unlock_rescan_remove();
> hbus->state = hv_pcibus_installed;
> return 0;
> }
> @@ -4003,6 +4007,9 @@ static struct hv_driver hv_pci_drv = {
> .remove = hv_pci_remove,
> .suspend = hv_pci_suspend,
> .resume = hv_pci_resume,
> + .driver = {
> + .probe_type = PROBE_PREFER_ASYNCHRONOUS,
> + },
> };
>
> static void __exit exit_hv_pci_drv(void)
> --
> 2.25.1
Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
