linux-kernel - Re: [PATCH 4/5] PCI: only return true when dev io state is really changed

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Date:   Fri, 25 Sep 2020 15:38:06 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Ethan Zhao <haifeng.zhao@...el.com>
Cc:     bhelgaas@...gle.com, oohall@...il.com, ruscur@...sell.cc,
        lukas@...ner.de, stuart.w.hayes@...il.com, mr.nuke.me@...il.com,
        mika.westerberg@...ux.intel.com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, pei.p.jia@...el.com
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