Re: [PATCH v1 1/1] PCI/ERR: don't clobber status after reset_link()

[Hedi Berriche]

On Fri, Oct 09, 2020 at 05:09 Hedi Berriche wrote:
> On Fri, Oct 09, 2020 at 04:46 Raj, Ashok wrote:
>
> Hi Ashok,
>
> Thanks for looking into this.
>
> > On Fri, Oct 09, 2020 at 03:52:51AM +0100, Hedi Berriche wrote:
> > > Commit 6d2c89441571 ("PCI/ERR: Update error status after reset_link()")
> > > changed pcie_do_recovery() so that status is updated with the return
> > > value from reset_link(); this was to fix the problem where we would
> > > wrongly report recovery failure, despite a successful reset_link(),
> > > whenever the initial error status is PCI_ERS_RESULT_DISCONNECT or
> > > PCI_ERS_RESULT_NO_AER_DRIVER.
> > >
> > > Unfortunately this breaks the flow of pcie_do_recovery() as it prevents
> >
> > What is the reference to "this breaks" above?
>
> The code change introduced by commit 6d2c89441571; would
>
>    "this code change" instead of "this breaks"
>
> work better? If not, I can also rephrase the whole paragraph along the following lines:
>
> Commit 6d2c89441571 ("PCI/ERR: Update error status after reset_link()") breaks the flow
> of pcie_do_recovery() as it prevents the actions needed when the initial error is
> PCI_ERS_RESULT_CAN_RECOVER or PCI_ERS_RESULT_NEED_RESET from taking place which causes
> error recovery to fail.
>
> ... and do away with the first paragraph.
>
> > > the actions needed when the initial error is PCI_ERS_RESULT_CAN_RECOVER
> > > or PCI_ERS_RESULT_NEED_RESET from taking place which causes error
> > > recovery to fail.
> > >
> > > Don't clobber status after reset_link() to restore the intended flow in
> > > pcie_do_recovery().
> > >
> > > Fix the original problem by saving the return value from reset_link()
> > > and use it later on to decide whether error recovery should be deemed
> > > successful in the scenarios where the initial error status is
> > > PCI_ERS_RESULT_{DISCONNECT,NO_AER_DRIVER}.
> >
> > I would rather rephrase the above to make it clear what is being proposed.
> > Since the description seems to talk about the old problem and new solution
> > all mixed up.
>
> OK; will do that to clarify that what's being proposed here is:
>
>    1. fix the regression introduced by commit 6d2c89441571
>    2. address the problem that commit 6d2c89441571 aimed to fix
>
> > > Fixes: 6d2c89441571 ("PCI/ERR: Update error status after reset_link()")
> > > Signed-off-by: Hedi Berriche <hedi.berriche@xxxxxxx>
> > > Cc: Russ Anderson <rja@xxxxxxx>
> > > Cc: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> > > Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> > > Cc: Ashok Raj <ashok.raj@xxxxxxxxx>
> > > Cc: Keith Busch <keith.busch@xxxxxxxxx>
> > > Cc: Joerg Roedel <jroedel@xxxxxxxx>
> > >
> > > Cc: stable@xxxxxxxxxx # v5.7+
> > > ---
> > > drivers/pci/pcie/err.c | 13 ++++++++++---
> > > 1 file changed, 10 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
> > > index c543f419d8f9..dbd0b56bd6c1 100644
> > > --- a/drivers/pci/pcie/err.c
> > > +++ b/drivers/pci/pcie/err.c
> > > @@ -150,7 +150,7 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> > > 			pci_channel_state_t state,
> > > 			pci_ers_result_t (*reset_link)(struct pci_dev *pdev))
> > > {
> > > -	pci_ers_result_t status = PCI_ERS_RESULT_CAN_RECOVER;
> > > +	pci_ers_result_t post_reset_status, status = PCI_ERS_RESULT_CAN_RECOVER;
> >
> > why call it post_reset_status?
>
> Perhaps post_reset_status is not a great choice; would reset_result or reset_link_result be better?

... or just do this with a boolean instead as I had it in an earlier iteration of the patch before I
eventually opted to use an pci_ers_result_t.

Cheers,
Hedi.
> Cheers,
> Hedi.
>
> > > 	struct pci_bus *bus;
> > >
> > > 	/*
> > > @@ -165,8 +165,8 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> > > 	pci_dbg(dev, "broadcast error_detected message\n");
> > > 	if (state == pci_channel_io_frozen) {
> > > 		pci_walk_bus(bus, report_frozen_detected, &status);
> > > -		status = reset_link(dev);
> > > -		if (status != PCI_ERS_RESULT_RECOVERED) {
> > > +		post_reset_status = reset_link(dev);
> > > +		if (post_reset_status != PCI_ERS_RESULT_RECOVERED) {
> > > 			pci_warn(dev, "link reset failed\n");
> > > 			goto failed;
> > > 		}
> > > @@ -174,6 +174,13 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> > > 		pci_walk_bus(bus, report_normal_detected, &status);
> > > 	}
> > >
> > > +	if ((status == PCI_ERS_RESULT_DISCONNECT ||
> > > +	     status == PCI_ERS_RESULT_NO_AER_DRIVER) &&
> > > +	     post_reset_status == PCI_ERS_RESULT_RECOVERED) {
> > > +		/* error recovery succeeded thanks to reset_link() */
> > > +		status = PCI_ERS_RESULT_RECOVERED;
> > > +	}
> > > +
> > > 	if (status == PCI_ERS_RESULT_CAN_RECOVER) {
> > > 		status = PCI_ERS_RESULT_RECOVERED;
> > > 		pci_dbg(dev, "broadcast mmio_enabled message\n");
> > > --
> > > 2.28.0
>
> --
> Be careful of reading health books, you might die of a misprint.
> 	-- Mark Twain

--
Be careful of reading health books, you might die of a misprint.
	-- Mark Twain