On 1/11/21 5:37 PM, Keith Busch wrote:
> On Mon, Jan 11, 2021 at 02:39:20PM +0100, Hinko Kocevar wrote:
>> Testing this patch a bit more (without the 5/5) resulted in the same CPU
>> lockup:
>>
>> watchdog: BUG: soft lockup - CPU#2 stuck for 22s! [irq/122-aerdrv:128]
>>
>> as I initially reported with the 5/5 of this patch included.
>>
>> It seems more infrequent, though. For example, after reboot this is not
>> observed and the recovery process is successful, whereas when 5/5 is also
>> used every recovery resulted in CPU lockup.
> 
> I am assuming this soft lockup is still when restoring the downstream
> port's virtual channel capability. Your initial sighting indicates that
> it doesn't appear to be a deadlock, but the stack trace never existed
> pci_restore_vc_state() either. I did not find any obvious issues here
> just from code inspection, so if you could try applying the following
> patch and send the kernel messages output, that would help.
> 
> ---
> diff --git a/drivers/pci/vc.c b/drivers/pci/vc.c
> index 5fc59ac31145..4834af7eb582 100644
> --- a/drivers/pci/vc.c
> +++ b/drivers/pci/vc.c
> @@ -28,6 +28,7 @@ static void pci_vc_save_restore_dwords(struct pci_dev *dev, int pos,
>   {
>   	int i;
>   
> +	pci_warn(dev, "%s: pos:%d dwords:%d\n", __func__, pos, dwords);
>   	for (i = 0; i < dwords; i++, buf++) {
>   		if (save)
>   			pci_read_config_dword(dev, pos + (i * 4), buf);
> @@ -110,6 +111,8 @@ static void pci_vc_enable(struct pci_dev *dev, int pos, int res)
>   	if (!pci_is_pcie(dev) || !pcie_downstream_port(dev))
>   		return;
>   
> +	pci_warn(dev, "%s: pos:%d res:%d\n", __func__, pos, res);
> +
>   	ctrl_pos = pos + PCI_VC_RES_CTRL + (res * PCI_CAP_VC_PER_VC_SIZEOF);
>   	status_pos = pos + PCI_VC_RES_STATUS + (res * PCI_CAP_VC_PER_VC_SIZEOF);
>   
> @@ -165,6 +168,8 @@ static void pci_vc_enable(struct pci_dev *dev, int pos, int res)
>   	if (link && !pci_wait_for_pending(link, status_pos2,
>   					  PCI_VC_RES_STATUS_NEGO))
>   		pci_err(link, "VC%d negotiation stuck pending\n", id);
> +
> +	pci_warn(dev, "%s: pos:%d res:%d return\n", __func__, pos, res);
>   }
>   
>   /**
> @@ -190,6 +195,7 @@ static int pci_vc_do_save_buffer(struct pci_dev *dev, int pos,
>   	int i, len = 0;
>   	u8 *buf = save_state ? (u8 *)save_state->cap.data : NULL;
>   
> +	pci_warn(dev, "%s: buf:%d pos:%d\n", __func__, buf != NULL, pos);
>   	/* Sanity check buffer size for save/restore */
>   	if (buf && save_state->cap.size !=
>   	    pci_vc_do_save_buffer(dev, pos, NULL, save)) {
> @@ -278,6 +284,8 @@ static int pci_vc_do_save_buffer(struct pci_dev *dev, int pos,
>   		pci_read_config_dword(dev, pos + PCI_VC_RES_CAP +
>   				      (i * PCI_CAP_VC_PER_VC_SIZEOF), &cap);
>   		parb_offset = ((cap & PCI_VC_RES_CAP_ARB_OFF) >> 24) * 16;
> +		pci_warn(dev, "%s: i:%d evcc:%d parb_offset:%d\n", __func__, i,
> +			 evcc, parb_offset);
>   		if (parb_offset) {
>   			int size, parb_phases = 0;
>   
> @@ -332,6 +340,7 @@ static int pci_vc_do_save_buffer(struct pci_dev *dev, int pos,
>   		len += 4;
>   	}
>   
> +	pci_warn(dev, "%s: len:%d\n", __func__, len);
>   	return buf ? 0 : len;
>   }
>   
> @@ -399,6 +408,7 @@ void pci_restore_vc_state(struct pci_dev *dev)
>   		if (!save_state || !pos)
>   			continue;
>   
> +		pci_warn(dev, "%s: i:%d pos:%d\n", __func__, i, pos);
>   		pci_vc_do_save_buffer(dev, pos, save_state, false);
>   	}
>   }
> --
> 

Attached are the messages.

Thanks!