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

[Gavin Shan <gwshan@linux.vnet.ibm.com>]

On Thu, Apr 20, 2017 at 11:03:57AM +1000, Russell Currey wrote:
>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 <aik@ozlabs.ru>
>> > Signed-off-by: Russell Currey <ruscur@russell.cc>
>> > ---
>> > 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.
>

Yeah, avoiding unnecessary goto is always nice. I give my RB in another
reply.

Thanks,
Gavin

>> 
>> > 	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
>> 
>