Subject: Re: [PATCH v3 2/2] powerpc/eeh: Clean up and document event handling functions

From: Russell Currey <[email-masked]>
Date: Thu, 20 Apr 2017 11:03:57 +1000

On Thu, 2017-04-20 at 09:48 +1000, Gavin Shan wrote:
> On Wed, Apr 19, 2017 at 05:39:27PM +1000, Russell Currey wrote:
> > Remove unnecessary tags in eeh_handle_normal_event(), and add function
> > comments for eeh_handle_normal_event() and eeh_handle_special_event().
> > 
> > The only functional difference is that in the case of a PE reaching the
> > maximum number of failures, rather than one message telling you of this
> > and suggesting you reseat the device, there are two separate messages.
> > 
> > Suggested-by: Alexey Kardashevskiy <[email-masked]>
> > Signed-off-by: Russell Currey <[email-masked]>
> > ---
> > V3: new.  Thanks to Alexey for the suggestions.
> > ---
> > arch/powerpc/kernel/eeh_driver.c | 36 ++++++++++++++++++++++++------------
> > 1 file changed, 24 insertions(+), 12 deletions(-)
> > 
> > diff --git a/arch/powerpc/kernel/eeh_driver.c
> > b/arch/powerpc/kernel/eeh_driver.c
> > index e50d1470714f..c405c79e50cd 100644
> > --- a/arch/powerpc/kernel/eeh_driver.c
> > +++ b/arch/powerpc/kernel/eeh_driver.c
> > @@ -724,6 +724,15 @@ static int eeh_reset_device(struct eeh_pe *pe, struct
> > pci_bus *bus,
> >  */
> > #define MAX_WAIT_FOR_RECOVERY 300
> > 
> > +/**
> > + * eeh_handle_normal_event - Handle EEH events on a specific PE
> > + * @pe: EEH PE
> > + *
> > + * Attempts to recover the given PE.  If recovery fails or the PE has
> > failed
> > + * too many times, remove the PE.
> > + *
> > + * Returns true if @pe should no longer be used, else false.
> > + */
> 
> I think this bit of comments would be part of PATCH[1/2]? Also, the
> comments needn't to be in any document as it's static one. I guess
> you might not want it to show in stable branches as PATCH[1/2] has
> been tagged as stable. It's fine if that's the case.

Yeah, I asked mpe about this and he said it's easier to get things into stable
if they are purely fixes.

> 
> > static bool eeh_handle_normal_event(struct eeh_pe *pe)
> > {
> > 	struct pci_bus *frozen_bus;
> > @@ -741,8 +750,13 @@ static bool eeh_handle_normal_event(struct eeh_pe *pe)
> > 
> > 	eeh_pe_update_time_stamp(pe);
> > 	pe->freeze_count++;
> > -	if (pe->freeze_count > eeh_max_freezes)
> > -		goto excess_failures;
> > +	if (pe->freeze_count > eeh_max_freezes) {
> > +		pr_err("EEH: PHB#%x-PE#%x has failed %d times in the\n"
> > +		       "last hour and has been permanently disabled.\n",
> > +		       pe->phb->global_number, pe->addr,
> > +		       pe->freeze_count);
> > +		goto hard_fail;
> > +	}
> > 	pr_warn("EEH: This PCI device has failed %d times in the last hour\n",
> > 		pe->freeze_count);
> > 
> > @@ -872,25 +886,16 @@ static bool eeh_handle_normal_event(struct eeh_pe *pe)
> > 
> > 	return false;
> > 
> > -excess_failures:
> > +hard_fail:
> > 	/*
> > 	 * About 90% of all real-life EEH failures in the field
> > 	 * are due to poorly seated PCI cards. Only 10% or so are
> > 	 * due to actual, failed cards.
> > 	 */
> 
> This bit of comments apply to "excess_failures" only, so it would
> be moved together with the pr_err(). Frankly speaking, I don't see
> the benebit of the cleanup. "excess_failure" in the original code
> indicates the case (excessive failures) explicitly, which is nice.
> However, it's not a big deal.

It applies to anything mentioning "reseating or replacing", which used to be two
 print statements but with this patch is only one.

> 
> > -	pr_err("EEH: PHB#%x-PE#%x has failed %d times in the\n"
> > -	       "last hour and has been permanently disabled.\n"
> > -	       "Please try reseating or replacing it.\n",
> > -		pe->phb->global_number, pe->addr,
> > -		pe->freeze_count);
> > -	goto perm_error;
> > -
> > -hard_fail:
> > 	pr_err("EEH: Unable to recover from failure from PHB#%x-PE#%x.\n"
> > 	       "Please try reseating or replacing it\n",
> > 		pe->phb->global_number, pe->addr);
> > 
> > -perm_error:
> 
> We will have the message from above pr_err() for "perm_error" case, but
> we don't have that in original code.

Yes, there's a slight difference here.  I chose to print two messages in the
excess failures case, one stating that the failure as been hit and then also
printing the general permanent failure message.  I don't think it makes much of
a difference, and it saves a tag.  I definitely like only having one goto in the
function.

Thanks for the review.

> 
> > 	eeh_slot_error_detail(pe, EEH_LOG_PERM);
> > 
> > 	/* Notify all devices that they're about to go down. */
> > @@ -923,6 +928,13 @@ static bool eeh_handle_normal_event(struct eeh_pe *pe)
> > 	return false;
> > }
> > 
> > +/**
> > + * eeh_handle_special_event - Handle EEH events without a specific failing
> > PE
> > + *
> > + * Called when an EEH event is detected but can't be narrowed down to a
> > + * specific PE.  Iterates through possible failures and handles them as
> > + * necessary.
> > + */
> > static void eeh_handle_special_event(void)
> > {
> > 	struct eeh_pe *pe, *phb_pe;
> 
> Thanks,
> Gavin
>