Subject: Re: [RESEND,v3] powerpc/pseries: Limit EPOW reset event warnings

From: Vipin K Parashar <[email-masked]>
Date: Fri, 17 Jul 2015 15:21:29 +0530

On 07/16/2015 09:35 AM, Michael Ellerman wrote:
> On Wed, 2015-15-07 at 04:22:06 UTC, Kamalesh Babulal wrote:
>> Kernel prints respective warnings about various EPOW events for
>> user information/action after parsing EPOW interrupts.Prompting
>> user to take action depending upon the severity of the event.
>>
>> At times EPOW reset event warning, such as below could flood
>> 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
>> May 25 04:04:24 alp kernel: Non critical power or cooling issue cleared
>> May 25 04:07:18 alp kernel: Non critical power or cooling issue cleared
>> May 25 04:13:04 alp kernel: Non critical power or cooling issue cleared
>> May 25 04:22:04 alp kernel: Non critical power or cooling issue cleared
>> May 25 04:22:26 alp kernel: Non critical power or cooling issue cleared
>> May 25 04:22:36 alp kernel: Non critical power or cooling issue cleared
>>
>> This patch avoids these multiple EPOW reset warnings by using a boolean
>> flag. This flag is initialized to false and is set to true upon arrival
>> of EPOW event. This same flag is checked and reset during EPOW_RESET
>> scenario to filter out valid EPOW reset events and avoid multiple warning
>> logs.
> Why are we even getting these reset events when nothing has happened?
>
>> Also, merged adjacent pr_err/pr_emerg into single one to reduce
>> the number of lines printed per warning.
>>
>> Suggested-by: Vipin K Parashar <[email-masked]>
>> [Vipin: edited the changelog]
>> Cc: Anshuman Khandual <[email-masked]>
>> Cc: Anton Blanchard <[email-masked]>
>> Cc: Michael Ellerman <[email-masked]>
>> Signed-off-by: Kamalesh Babulal <[email-masked]>
>> ---
>> 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 | 25 +++++++++++++++++--------
>>   1 file changed, 17 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/powerpc/platforms/pseries/ras.c b/arch/powerpc/platforms/pseries/ras.c
>> index 02e4a17..b30396a 100644
>> --- a/arch/powerpc/platforms/pseries/ras.c
>> +++ b/arch/powerpc/platforms/pseries/ras.c
>> @@ -40,6 +40,9 @@ static int ras_check_exception_token;
>>   #define EPOW_SENSOR_TOKEN	9
>>   #define EPOW_SENSOR_INDEX	0
>>   
>> +/* Flag to limit EPOW RESET warning. */
>> +static bool epow_state;
> This name is terrible, it doesn't give me any hint to what it means.
>
> But really it should be a counter, not a boolean.
>
> We could have multiple EPOW events come in and then later get the reset events
> for them, couldn't we?

As per PAPR i see below description of EPOW_RESET

EPOW_RESET / MESSAGE (0)  - No EPOW event is pending.

So we probably need to understand if it is send only after all EPOW 
events have
reset or just last EPOW event. From the PAPR description is seems to be 
first case.

>
>
> So what about:
>
> static unsigned epow_event_depth;
>
> And then below:
>
>> @@ -145,21 +148,27 @@ static void rtas_parse_epow_errlog(struct rtas_error_log *log)
>>   
> 	epow_event_depth++;
>
>    	switch (action_code) {
>    	case EPOW_RESET:
> 		if (epow_event_depth)
> 			epow_event_depth--;
>
> 		if (epow_event_depth)
>> +			pr_err("Non critical power or cooling issue cleared");
>>   		break;
>
> And that's all you need.
>
>
>>   	case EPOW_WARN_COOLING:
>> -		pr_err("Non critical cooling issue reported by firmware");
>> -		pr_err("Check RTAS error log for details");
>> +		pr_err("Non critical cooling issue reported by firmware, "
>> +		       "Check RTAS error log for details");
> This should be:
>
> 		pr_err("Non-critical cooling issue reported by firmware, check RTAS error log for details.\n");
>
> But that's too long, so how about:
>
> 		pr_err("Non-critical cooling issue reported, check RTAS error log for details.\n");
>
> And if it's non-critical it shouldn't be pr_err(), it should be pr_info().
>
> Similarly for all the other messages.
>
>
> cheers
>