Re: [PATCH 3/4] PCI/hotplug: reset_lock is not required synchronizing with irq thread

Lukas Wunner
2025-03-14T08:32:49Z

On Thu, Mar 13, 2025 at 04:23:32PM +0200, Ilpo Järvinen wrote:
> Disabling HPIE (Hot-Plug Interrupt Enable) and synchronizing with irq
> handling in pciehp_reset_slot() is enough to ensure no pending events
> are processed during the slot reset. Thus, there is no need to take
> reset_lock in the IRQ thread.
[...]
> --- a/drivers/pci/hotplug/pciehp_hpc.c
> +++ b/drivers/pci/hotplug/pciehp_hpc.c
> @@ -748,12 +748,10 @@ static irqreturn_t pciehp_ist(int irq, void *dev_id)
> * Disable requests have higher priority than Presence Detect Changed
> * or Data Link Layer State Changed events.
> */
> - down_read_nested(&ctrl->reset_lock, ctrl->depth);
> if (events & DISABLE_SLOT)
> pciehp_handle_disable_request(ctrl);
> else if (events & (PCI_EXP_SLTSTA_PDC | PCI_EXP_SLTSTA_DLLSC))
> pciehp_handle_presence_or_link_change(ctrl, events);
> - up_read(&ctrl->reset_lock);
>
> ret = IRQ_HANDLED;
> out:

The release and re-acquisition of reset_lock in
pciehp_configure_device() and pciehp_unconfigure_device()
needs to be removed as well if the above hunk is applied.

But please wait a little while before respinning so that I can
think through the whole series.

Thanks,

Lukas