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

Zhao, Haifeng
2020-09-27T01:28:59Z

Yes, better !

-----Original Message-----
From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
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.intel.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
> 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;

?