linux-kernel - Re: [PATCH 4/5 V4] PCI: only return true when dev io state is really changed

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Message-ID: <CAHp75VfRaQfdL130xzGXhHjCNfC2hAmH3PM7jKqGPBGTgsK+Aw@mail.gmail.com>
Date:   Mon, 28 Sep 2020 11:46:27 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Ethan Zhao <haifeng.zhao@...el.com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, Oliver <oohall@...il.com>,
        ruscur@...sell.cc, Lukas Wunner <lukas@...ner.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Stuart Hayes <stuart.w.hayes@...il.com>,
        Alexandru Gagniuc <mr.nuke.me@...il.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        linux-pci <linux-pci@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        pei.p.jia@...el.com, ashok.raj@...ux.intel.com,
        Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@...el.com>
Subject: Re: [PATCH 4/5 V4] PCI: only return true when dev io state is really changed

On Mon, Sep 28, 2020 at 7:13 AM Ethan Zhao <haifeng.zhao@...el.com> 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.
>

This one looks good (more or less) now.
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>

> 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>
> Reviewed-by: Alexandru Gagniuc <mr.nuke.me@...il.com>
> ---
> Changnes:
>  V2: revise description and code according to suggestion from Andy.
>  V3: change code to simpler.
>  V4: no change.
>  V5: no change.
>
>  drivers/pci/pci.h | 37 +++++--------------------------------
>  1 file changed, 5 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index fa12f7cbc1a0..a2c1c7d5f494 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -359,39 +359,12 @@ struct pci_sriov {
>  static inline bool pci_dev_set_io_state(struct pci_dev *dev,
>                                         pci_channel_state_t new)
>  {
> -       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)
> -               dev->error_state = new;
> -       return changed;
> +       if (dev->error_state == new)
> +               return false;
> +
> +       dev->error_state = new;
> +       return true;
>  }
>
>  static inline int pci_dev_set_disconnected(struct pci_dev *dev, void *unused)
> --
> 2.18.4
>


-- 
With Best Regards,
Andy Shevchenko