RE: [PATCH 4/5] PCI: only return true when dev io state is really changed

[Zhao, Haifeng]

Yes, better ! 

-----Original Message-----
From: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> 
Sent: Friday, September 25, 2020 8:38 PM
To: Zhao, Haifeng <haifeng.zhao@xxxxxxxxx>
Cc: bhelgaas@xxxxxxxxxx; oohall@xxxxxxxxx; ruscur@xxxxxxxxxx; lukas@xxxxxxxxx; stuart.w.hayes@xxxxxxxxx; mr.nuke.me@xxxxxxxxx; mika.westerberg@xxxxxxxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Jia, Pei P <pei.p.jia@xxxxxxxxx>
Subject: Re: [PATCH 4/5] PCI: only return true when dev io state is really changed

On Thu, Sep 24, 2020 at 10:34:22PM -0400, Ethan Zhao wrote:
> When uncorrectable error happens, AER driver and DPC driver interrupt 
> handlers likely call
>    pcie_do_recovery()->pci_walk_bus()->report_frozen_detected() with 
> pci_channel_io_frozen the same time.

Call chains are better to read if they split like

   foo() ->
     bar() ->
       baz()

>    If pci_dev_set_io_state() return true even if the original state is 
> pci_channel_io_frozen, that will cause AER or DPC handler re-enter the 
> error detecting and recovery procedure one after another.
>    The result is the recovery flow mixed between AER and DPC.
> So simplify the pci_dev_set_io_state() function to only return true 
> when dev->error_state is changed.

...

> +	if (dev->error_state != new) {
>  		dev->error_state = new;
> +		changed = true;
> +	}
>  	return changed;

Perhaps
	if (dev->error_state == new)
		return changed;

	dev->error_state = new;
	return true;

?


--
With Best Regards,
Andy Shevchenko