linux-kernel - Re: [PATCH 2/5 V2] PCI: pciehp: check and wait port status out of DPC before handling DLLSC and PDC

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Date:   Sun, 27 Sep 2020 11:27:46 -0400
From:   Sinan Kaya <okaya@...nel.org>
To:     Ethan Zhao <haifeng.zhao@...el.com>, bhelgaas@...gle.com,
        oohall@...il.com, ruscur@...sell.cc, lukas@...ner.de,
        andriy.shevchenko@...ux.intel.com, stuart.w.hayes@...il.com,
        mr.nuke.me@...il.com, mika.westerberg@...ux.intel.com,
        Keith Busch <keith.busch@...el.com>
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        pei.p.jia@...el.com, ashok.raj@...ux.intel.com,
        sathyanarayanan.kuppuswamy@...el.com
Subject: Re: [PATCH 2/5 V2] PCI: pciehp: check and wait port status out of DPC
 before handling DLLSC and PDC

On 9/26/2020 11:28 PM, Ethan Zhao wrote:
> diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
> index 53433b37e181..6f271160f18d 100644
> --- a/drivers/pci/hotplug/pciehp_hpc.c
> +++ b/drivers/pci/hotplug/pciehp_hpc.c
> @@ -710,8 +710,10 @@ static irqreturn_t pciehp_ist(int irq, void *dev_id)
>  	down_read(&ctrl->reset_lock);
>  	if (events & DISABLE_SLOT)
>  		pciehp_handle_disable_request(ctrl);
> -	else if (events & (PCI_EXP_SLTSTA_PDC | PCI_EXP_SLTSTA_DLLSC))
> +	else if (events & (PCI_EXP_SLTSTA_PDC | PCI_EXP_SLTSTA_DLLSC)) {
> +		pci_wait_port_outdpc(pdev);
>  		pciehp_handle_presence_or_link_change(ctrl, events);
> +	}
>  	up_read(&ctrl->reset_lock);

This looks like a hack TBH.

Lukas, Keith;

What is your take on this?
Why is device lock not protecting this situation?

Is there a lock missing in hotplug driver?

Sinan