Re: [PATCH v.23-2] RAS: use tracepoint to handle hw issues

[Borislav Petkov]

>From Documentation/SubmittingPatches:

"2) Describe your changes.

Describe the technical detail of the change(s) your patch includes.

Be as specific as possible."

"use tracepoint to handle hw issues" is not specific - it is bullshit
bingo with a random word generator.

I'm getting tired of this crap: either take the suggestion as is,
without randomly changing it for no reason whatsoever, or give a good
reason why it is not a good suggestion and propose a better one!

Randomly changing it in the next version of the patch for another, even
crappier one doesn't help.

On Fri, May 11, 2012 at 11:54:14AM -0300, Mauro Carvalho Chehab wrote:
> Add a new tracepoint-based hardware events report method for
> reporting Memory Controller events.
> 
> Part of the description bellow is shamelessly copied from Tony
> Luck's notes about the Hardware Error BoF during LPC 2010 [1].
> Tony, thanks for your notes and discussions to generate the
> h/w error reporting requirements.
> 
> [1] http://lwn.net/Articles/416669/
> 
>     We have several subsystems & methods for reporting hardware errors:
> 
>     1) EDAC ("Error Detection and Correction").  In its original form
>     this consisted of a platform specific driver that read topology
>     information and error counts from chipset registers and reported
>     the results via a sysfs interface.
> 
>     2) mcelog - x86 specific decoding of machine check bank registers
>     reporting in binary form via /dev/mcelog. Recent additions make use
>     of the APEI extensions that were documented in version 4.0a of the
>     ACPI specification to acquire more information about errors without
>     having to rely reading chipset registers directly. A user level
>     programs decodes into somewhat human readable format.
> 
>     3) drivers/edac/mce_amd.c - this driver hooks into the mcelog path and
>     decodes errors reported via machine check bank registers in AMD
>     processors to the console log using printk();
> 
>     Each of these mechanisms has a band of followers ... and none
>     of them appear to meet all the needs of all users.
> 
> As part of a RAS subsystem, let's encapsulate the memory error hardware
> events into a trace facility.
> 
> The tracepoint printk will be displayed like:
> 
> mc_event: (Corrected|Uncorrected|Fatal) error:[error msg] on memory stick "[label]" ([location] [edac_mc detail] [driver_detail])
> 
> Where:
> 	[error msg] is the driver-specific error message
> 		    (e. g. "memory read", "bus error", ...);
> 	[location] is the location in terms of memory controller and
> 		   branch/channel/slot, channel/slot or csrow/channel;
> 	[label] is the memory stick label;
> 	[edac_mc detail] describes the address location of the error
> 			 and the syndrome;
> 	[driver detail] is driver-specifig error message details,
> 			when needed/provided (e. g. "area:DMA", ...)
> 
> For example:
> 
> mc_event: Corrected error:memory read on memory stick "DIMM_1A" (mc:0 channel:0 slot:0 page:0x586b6e offset:0xa66 grain:32 syndrome:0x0 area:DMA)
> 
> Of course, any userspace tools meant to handle errors should not parse
> the above data. They should, instead, use the binary fields provided by
> the tracepoint, mapping them directly into their MIBs.
> 
> NOTE: The original patch was providing an additional mechanism for
> MCA-based trace events that also contained MCA error register data.
> Hoever, as no agreement was reached so far for the MCA-based trace
> events, for now, let's add events only for memory errors.
> A latter patch is planned to change the tracepoint, for those types
> of event.
> 
> Reviewed-by: Aristeu Rozanski <arozansk@xxxxxxxxxx>
> Cc: Doug Thompson <norsk5@xxxxxxxxx>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
> ---
>  drivers/edac/edac_core.h |    2 +-
>  drivers/edac/edac_mc.c   |   25 ++++++++++----
>  include/ras/ras_event.h  |   78 ++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 97 insertions(+), 8 deletions(-)
>  create mode 100644 include/ras/ras_event.h
> 
> diff --git a/drivers/edac/edac_core.h b/drivers/edac/edac_core.h
> index f06ce9a..eee7360 100644
> --- a/drivers/edac/edac_core.h
> +++ b/drivers/edac/edac_core.h
> @@ -468,7 +468,7 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
>  			  const int layer2,
>  			  const char *msg,
>  			  const char *other_detail,
> -			  const void *mcelog);
> +			  const void *arch_log);
>  
>  /*
>   * edac_device APIs
> diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
> index e5b5563..0153cd98 100644
> --- a/drivers/edac/edac_mc.c
> +++ b/drivers/edac/edac_mc.c
> @@ -33,6 +33,10 @@
>  #include "edac_core.h"
>  #include "edac_module.h"
>  
> +#define CREATE_TRACE_POINTS
> +#define TRACE_INCLUDE_PATH ../../include/ras
> +#include <ras/ras_event.h>
> +
>  /* lock to memory controller's control array */
>  static DEFINE_MUTEX(mem_ctls_mutex);
>  static LIST_HEAD(mc_devices);
> @@ -381,6 +385,7 @@ struct mem_ctl_info *edac_mc_alloc(unsigned mc_num,
>  	 * which will perform kobj unregistration and the actual free
>  	 * will occur during the kobject callback operation
>  	 */
> +
>  	return mci;
>  }
>  EXPORT_SYMBOL_GPL(edac_mc_alloc);
> @@ -982,7 +987,7 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
>  			  const int layer2,
>  			  const char *msg,
>  			  const char *other_detail,
> -			  const void *mcelog)
> +			  const void *arch_log)
>  {
>  	/* FIXME: too much for stack: move it to some pre-alocated area */
>  	char detail[80], location[80];
> @@ -1119,21 +1124,27 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
>  	}
>  
>  	/* Memory type dependent details about the error */
> -	if (type == HW_EVENT_ERR_CORRECTED) {
> +	if (type == HW_EVENT_ERR_CORRECTED)
>  		snprintf(detail, sizeof(detail),
>  			"page:0x%lx offset:0x%lx grain:%d syndrome:0x%lx",
>  			page_frame_number, offset_in_page,
>  			grain, syndrome);
> -		edac_ce_error(mci, pos, msg, location, label, detail,
> -			      other_detail, enable_per_layer_report,
> -			      page_frame_number, offset_in_page, grain);
> -	} else {
> +	else
>  		snprintf(detail, sizeof(detail),
>  			"page:0x%lx offset:0x%lx grain:%d",
>  			page_frame_number, offset_in_page, grain);
>  
> +	/* Report the error via the trace interface */
> +	trace_mc_event(type, mci->mc_idx, msg, label, location,
> +		       detail, other_detail);
> +
> +	/* Report the error via the edac_mc_printk() interface */
> +	if (type == HW_EVENT_ERR_CORRECTED)
> +		edac_ce_error(mci, pos, msg, location, label, detail,
> +			      other_detail, enable_per_layer_report,
> +			      page_frame_number, offset_in_page, grain);
> +	else
>  		edac_ue_error(mci, pos, msg, location, label, detail,
>  			      other_detail, enable_per_layer_report);
> -	}
>  }
>  EXPORT_SYMBOL_GPL(edac_mc_handle_error);
> diff --git a/include/ras/ras_event.h b/include/ras/ras_event.h
> new file mode 100644
> index 0000000..66f6a43
> --- /dev/null
> +++ b/include/ras/ras_event.h
> @@ -0,0 +1,78 @@
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM ras
> +#define TRACE_INCLUDE_FILE ras_event
> +
> +#if !defined(_TRACE_HW_EVENT_MC_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_HW_EVENT_MC_H
> +
> +#include <linux/tracepoint.h>
> +#include <linux/edac.h>
> +#include <linux/ktime.h>
> +
> +/*
> + * Hardware Events Report
> + *
> + * Those events are generated when hardware detected a corrected or
> + * uncorrected event, and are meant to replace the current API to report
> + * errors defined on both EDAC and MCE subsystems.
> + *
> + * FIXME: Add events for handling memory errors originated from the
> + *        MCE subsystem.
> + */
> +
> +/*
> + * Hardware-independent Memory Controller specific events
> + */
> +
> +/*
> + * Default error mechanisms for Memory Controller errors (CE and UE)
> + */
> +TRACE_EVENT(mc_event,
> +
> +	TP_PROTO(const unsigned int err_type,
> +		 const unsigned int mc_index,
> +		 const char *error_msg,
> +		 const char *label,
> +		 const char *location,
> +		 const char *core_detail,
> +		 const char *driver_detail),
> +
> +	TP_ARGS(err_type, mc_index, error_msg, label, location,
> +		core_detail, driver_detail),
> +
> +	TP_STRUCT__entry(
> +		__field(	unsigned int,	err_type		)
> +		__field(	unsigned int,	mc_index		)
> +		__string(	msg,		error_msg		)
> +		__string(	label,		label			)
> +		__string(	detail,		core_detail		)
> +		__string(	location,	location		)
> +		__string(	driver_detail,	driver_detail		)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->err_type		= err_type;
> +		__entry->mc_index		= mc_index;
> +		__assign_str(msg, error_msg);
> +		__assign_str(label, label);
> +		__assign_str(location, location);
> +		__assign_str(detail, core_detail);
> +		__assign_str(driver_detail, driver_detail);
> +	),
> +
> +	TP_printk("%s error:%s on memory stick \"%s\" (mc:%d %s %s %s)",
> +		  (__entry->err_type == HW_EVENT_ERR_CORRECTED) ? "Corrected" :
> +			((__entry->err_type == HW_EVENT_ERR_FATAL) ?
> +			"Fatal" : "Uncorrected"),
> +		  __get_str(msg),
> +		  __get_str(label),
> +		  __entry->mc_index,
> +		  __get_str(location),
> +		  __get_str(detail),
> +		  __get_str(driver_detail))
> +);
> +
> +#endif /* _TRACE_HW_EVENT_MC_H */
> +
> +/* This part must be outside protection */
> +#include <trace/define_trace.h>
> -- 
> 1.7.8
> 
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-- 
Regards/Gruss,
Boris.

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