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From:   "Zhao, Haifeng" <haifeng.zhao@intel.com>
To:     Andy Shevchenko <andriy.shevchenko@linux.intel.com>
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Subject: RE: [PATCH 4/5] PCI: only return true when dev io state is really
 changed
Thread-Topic: [PATCH 4/5] PCI: only return true when dev io state is really
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Date:   Sun, 27 Sep 2020 01:28:50 +0000
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Yes, better !=20

-----Original Message-----
From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>=20
Sent: Friday, September 25, 2020 8:38 PM
To: Zhao, Haifeng <haifeng.zhao@intel.com>
Cc: bhelgaas@google.com; oohall@gmail.com; ruscur@russell.cc; lukas@wunner.=
de; stuart.w.hayes@gmail.com; mr.nuke.me@gmail.com; mika.westerberg@linux.i=
ntel.com; linux-pci@vger.kernel.org; linux-kernel@vger.kernel.org; Jia, Pei=
 P <pei.p.jia@intel.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=20
> handlers likely call
>    pcie_do_recovery()->pci_walk_bus()->report_frozen_detected() with=20
> 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=20
> pci_channel_io_frozen, that will cause AER or DPC handler re-enter the=20
> 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=20
> when dev->error_state is changed.

...

> +	if (dev->error_state !=3D new) {
>  		dev->error_state =3D new;
> +		changed =3D true;
> +	}
>  	return changed;

Perhaps
	if (dev->error_state =3D=3D new)
		return changed;

	dev->error_state =3D new;
	return true;

?


--
With Best Regards,
Andy Shevchenko