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

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Date:   Sun, 27 Sep 2020 01:28:50 +0000
From:   "Zhao, Haifeng" <haifeng.zhao@...el.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
CC:     "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "oohall@...il.com" <oohall@...il.com>,
        "ruscur@...sell.cc" <ruscur@...sell.cc>,
        "lukas@...ner.de" <lukas@...ner.de>,
        "stuart.w.hayes@...il.com" <stuart.w.hayes@...il.com>,
        "mr.nuke.me@...il.com" <mr.nuke.me@...il.com>,
        "mika.westerberg@...ux.intel.com" <mika.westerberg@...ux.intel.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Jia, Pei P" <pei.p.jia@...el.com>
Subject: RE: [PATCH 4/5] PCI: only return true when dev io state is really
 changed

Yes, better ! 

-----Original Message-----
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com> 
Sent: Friday, September 25, 2020 8:38 PM
To: Zhao, Haifeng <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; Jia, Pei P <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