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 08:56:30 -0500
From:   "Alex G." <mr.nuke.me@...il.com>
To:     Ethan Zhao <haifeng.zhao@...el.com>, bhelgaas@...gle.com,
        oohall@...il.com, ruscur@...sell.cc, lukas@...ner.de,
        andriy.shevchenko@...ux.intel.com, stuart.w.hayes@...il.com,
        mika.westerberg@...ux.intel.com
Cc:     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

Hi Ethan,

On 9/24/20 9:34 PM, 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.
>     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.
> 
> Signed-off-by: Ethan Zhao <haifeng.zhao@...el.com>
> Tested-by: Wen jin <wen.jin@...el.com>
> Tested-by: Shanshan Zhang <ShanshanX.Zhang@...el.com>
> ---
>   drivers/pci/pci.h | 31 +++----------------------------
>   1 file changed, 3 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index fa12f7cbc1a0..d420bb977f3b 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -362,35 +362,10 @@ static inline bool pci_dev_set_io_state(struct pci_dev *dev,
>   	bool changed = false;
>   
>   	device_lock_assert(&dev->dev);
> -	switch (new) {
> -	case pci_channel_io_perm_failure:
> -		switch (dev->error_state) {
> -		case pci_channel_io_frozen:
> -		case pci_channel_io_normal:
> -		case pci_channel_io_perm_failure:
> -			changed = true;
> -			break;
> -		}
> -		break;
> -	case pci_channel_io_frozen:
> -		switch (dev->error_state) {
> -		case pci_channel_io_frozen:
> -		case pci_channel_io_normal:
> -			changed = true;
> -			break;
> -		}
> -		break;
> -	case pci_channel_io_normal:
> -		switch (dev->error_state) {
> -		case pci_channel_io_frozen:
> -		case pci_channel_io_normal:
> -			changed = true;
> -			break;
> -		}
> -		break;
> -	}
> -	if (changed)
> +	if (dev->error_state != new) {
>   		dev->error_state = new;
> +		changed = true;
> +	}
>   	return changed;
>   }

The flow is a lot easier to follow now. Thank you.

Reviewed-by: Alexandru Gagniuc <mr.nuke.me@...il.com>