Subject: Re: [PATCH v5] powerpc/pseries: Limit EPOW reset event warnings

From: Vipin K Parashar <[email-masked]>
Date: Mon, 30 Nov 2015 17:31:07 +0530

On Thursday 26 November 2015 02:50 PM, Vasant Hegde wrote:
> On 11/18/2015 02:12 PM, Vipin K Parashar wrote:
>> Kernel prints respective warnings about various EPOW events for
>> user information/action after parsing EPOW interrupts. At times
>> below EPOW reset event warning is seen to be flooding kernel log
>> over a period of time.
>>
>> May 25 03:46:34 alp kernel: Non critical power or cooling issue cleared
>> May 25 03:46:52 alp kernel: Non critical power or cooling issue cleared
>> May 25 03:53:48 alp kernel: Non critical power or cooling issue cleared
>> May 25 03:55:46 alp kernel: Non critical power or cooling issue cleared
>> May 25 03:56:34 alp kernel: Non critical power or cooling issue cleared
>> May 25 03:59:04 alp kernel: Non critical power or cooling issue cleared
>> May 25 04:02:01 alp kernel: Non critical power or cooling issue cleared
>>
> @Michael,
>   I think above log is raising some concern. We have been asked by multiple
> people on this. Hence I think we should avoid these duplicate messages.

Hi Michael,
          Please do let know if you have some suggestions with this patch.

>
>> These EPOW reset events are spurious in nature and are triggered by
>> firmware witout an actual EPOW event being reset. This patch avoids these
> s/witout/without/

sure, will edit.

>
>> multiple EPOW reset warnings by using a counter variable. This variable
>> is incremented every time an EPOW event is reported. Upon receiving a EPOW
>> reset event the same variable is checked to filer out spurious events and
>> decremented accordingly.
>>
>> This patch also improves log messages to better describe EPOW event being
>> reported. Merged adjacent log messages into single one to reduce number of
>> lines printed per event.
>>
>> Signed-off-by: Kamalesh Babulal<[email-masked]>
>> Signed-off-by: Vipin K Parashar<[email-masked]>
>> ---
>> v5 changes:
>>     - Used num_epow_events counter variable to count number of epow_events
>>     - Improved log messages to better describe epow event.
>>     - Merged adjacent warnings into single lines.
>>
>> v4 changes:
>>     - Changed the approach to depth counter to match the EPOW events and
>>       EPOW reset.
>>     - Converted pr_err() ot pr_info() for non-critical errors.
>>     - Merged adjacent warnings into single line across the file.
>>     - Fixed grammar in the warnings to make is short.
>>
>> v3 changes:
>>     - Limit warning printed by EPOW RESET event, by guarding it with bool flag.
>>       Instead of rate limiting all the EPOW events.
>>
>> v2 changes:
>>     - Merged multiple adjacent pr_err/pr_emerg into single line to reduce multi-line
>>       warnings, based on Michael's comments.
>>
>>   arch/powerpc/platforms/pseries/ras.c | 54 ++++++++++++++++++++----------------
>>   1 file changed, 30 insertions(+), 24 deletions(-)
>>
>> diff --git a/arch/powerpc/platforms/pseries/ras.c b/arch/powerpc/platforms/pseries/ras.c
>> index 3b6647e..bbe2856 100644
>> --- a/arch/powerpc/platforms/pseries/ras.c
>> +++ b/arch/powerpc/platforms/pseries/ras.c
>> @@ -40,6 +40,8 @@ static int ras_check_exception_token;
>>   #define EPOW_SENSOR_TOKEN	9
>>   #define EPOW_SENSOR_INDEX	0
>>   
>> +static int num_epow_events;
>> +
>>   static irqreturn_t ras_epow_interrupt(int irq, void *dev_id);
>>   static irqreturn_t ras_error_interrupt(int irq, void *dev_id);
>>   
>> @@ -82,32 +84,30 @@ static void handle_system_shutdown(char event_modifier)
>>   {
>>   	switch (event_modifier) {
>>   	case EPOW_SHUTDOWN_NORMAL:
>> -		pr_emerg("Firmware initiated power off");
>> +		pr_emerg("Power off requested\n");
> Why are you changing this  message? These are FW initiated Power off and helps
> us to identify who initiated shutdown request.

EPOW_SHUTDOWN_NORMAL event maps to DPO event in harwdare, which is received
upon system admin requesting LPAR poweroff. I felt that using FW 
initiated poweroff
phrase doesn't convey that poweroff was requested by a user so changed it.
        Please do suggest if you have something better to convey message.

>>   		orderly_poweroff(true);
>>   		break;
>>   
>>   	case EPOW_SHUTDOWN_ON_UPS:
>> -		pr_emerg("Loss of power reported by firmware, system is "
>> -			"running on UPS/battery");
>> -		pr_emerg("Check RTAS error log for details");
>> +		pr_emerg("Loss of system power detected. System is running on"
>> +			 " UPS/battery. Check RTAS error log for details\n");
>>   		orderly_poweroff(true);
>>   		break;
>>   
>>   	case EPOW_SHUTDOWN_LOSS_OF_CRITICAL_FUNCTIONS:
>> -		pr_emerg("Loss of system critical functions reported by "
>> -			"firmware");
>> -		pr_emerg("Check RTAS error log for details");
>> +		pr_emerg("Loss of system critical functions detected. Check"
>> +			 " RTAS error log for details\n");
>>   		orderly_poweroff(true);
>>   		break;
>>   
>>   	case EPOW_SHUTDOWN_AMBIENT_TEMPERATURE_TOO_HIGH:
>> -		pr_emerg("Ambient temperature too high reported by firmware");
>> -		pr_emerg("Check RTAS error log for details");
>> +		pr_emerg("High ambient temperature detected. Check RTAS"
>> +			 " error log for details\n");
>>   		orderly_poweroff(true);
>>   		break;
>>   
>>   	default:
>> -		pr_err("Unknown power/cooling shutdown event (modifier %d)",
>> +		pr_err("Unknown power/cooling shutdown event (modifier = %d)\n",
>>   			event_modifier);
>>   	}
>>   }
>> @@ -145,40 +145,47 @@ static void rtas_parse_epow_errlog(struct rtas_error_log *log)
>>   
>>   	switch (action_code) {
>>   	case EPOW_RESET:
>> -		pr_err("Non critical power or cooling issue cleared");
>> +		if (num_epow_events) {
>> +			pr_info("Non critical power/cooling issue cleared\n");
>> +			num_epow_events--;
>> +		}
>>   		break;
>>   
>>   	case EPOW_WARN_COOLING:
>> -		pr_err("Non critical cooling issue reported by firmware");
>> -		pr_err("Check RTAS error log for details");
>> +		pr_info("Non-critical cooling issue detected. Check RTAS error"
>> +			" log for details\n");
>> +		num_epow_events++;
> So every switch-case you are modifying this variable. Not sure this is the best way.
> How about adding if condition after switch to modify this variable ?

yeah i thought about it but dropped the idea as the variable isn't being 
incrementing
for all switch cases. Its only getting incremented for cases when we 
aren't doing system
poweroff. Though i can send out a patch with a single increment of the 
variable down
below the switch case as incrementing it for poweroff cases too would 
not no harm.

> -Vasant