Message-ID: <4FAA7649.5080606@redhat.com>
Date:	Wed, 09 May 2012 10:51:05 -0300
From:	Mauro Carvalho Chehab <mchehab@...hat.com>
To:	Borislav Petkov <bp@...64.org>
CC:	Linux Edac Mailing List <linux-edac@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Doug Thompson <norsk5@...oo.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>,
	Tony Luck <tony.luck@...el.com>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [EDAC ABI v13 04/25] events/hw_event: Create a Hardware Events
 Report Mecanism (HERM)

Em 09-05-2012 10:22, Borislav Petkov escreveu:
> + Tony.

C/C Steven.

> On Wed, May 09, 2012 at 09:50:10AM -0300, Mauro Carvalho Chehab wrote:
>> Em 09-05-2012 09:13, Borislav Petkov escreveu:
>>> Inserting the latest version:
>>>
>>>> From 4afb0250415e87b983f5937d456c83407fe96264 Mon Sep 17 00:00:00 2001
>>>> From: Mauro Carvalho Chehab <mchehab@...hat.com>
>>>> Date: Thu, 23 Feb 2012 08:10:34 -0300
>>>> Subject: [PATCH] events/hw_event: Create a Hardware Events Report Mecanism
>>>>  (HERM)
>>>
>>> Ok, let's face it: this is just a single trace_mc_error tracepoint,
>>> nothing else. Let's drop the HERM bullshit bingo and call the thing by
>>> it's name: "Add yet another tracepoint to report DRAM ECC errors".
>>
>> This name is nice and helps to distinguish this mechanism among others,
>> and will help to distinguish between HARM-aware userspace tools from the
>> existing ones.
> 
> This may be so but it is not a mechanism - it is simply using a kernel
> facility - a tracepoint - and that's it.

Ok, I'll then rename it to "Hardware Events Report Method".

> Now, if you really want to have a generic mechanism for RAS, used
> by all the kernel, then I don't have a problem with you adding it
> to include/ras/hw_event.h or somewhere in that vicinity along with
> making it generic enough for other users and then taking care of it and
> developing it to address users' needs.

I'm ok to move it to include/ras, but, if I remember well from my initial
tests when I wrote this, several kernel versions ago, there is/was
a limitation that required that all trace events should be under
include/trace/events/.

One other option would be to call it as "include/trace/events/ras.h".

Steven,

Would it be possible/recommendable to move this trace header
to include/linux/ras/hw_event.h?

In a matter of fact, my plan is to move the EDAC core to drivers/ras, after
making it generic enough.

> But simply growing stuff here and there for a specific use case is not
> the way to go.
> 
> [ … ]
> 
>>>> diff --git a/include/trace/events/hw_event.h b/include/trace/events/hw_event.h
>>>> new file mode 100644
>>>> index 000000000000..1fabfe21e29a
>>>> --- /dev/null
>>>> +++ b/include/trace/events/hw_event.h
>>>> @@ -0,0 +1,107 @@
>>>> +#undef TRACE_SYSTEM
>>>> +#define TRACE_SYSTEM hw_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 Anomaly Report Mecanism (HARM) events
>>>> + *
>>>> + * 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.
>>>> + */
>>>> +
>>>> +DECLARE_EVENT_CLASS(hw_event_class,
>>>
>>> Ok, event classes are for sharing tracepoints which have the same
>>> TP_PROTO, TP_ARGS.. etc arguments as Steven's (CCed) article on lwn
>>> points out.
>>
>> Other trace mechanisms will be added. One of them is the MCA-based tracepoint,
>> that got removed while no consensus is reached on that.
> 
> You're missing the point: are the other tracepoints using "const char
> *type" and "unsigned int instance" as arguments? No.
> 
> IOW, go look at http://lwn.net/Articles/381064/ for an example what the
> trace event class is. Hint: sched_wakeup and sched_wakeup_new.

I used that article when I wrote this code. Ok, the code is now very different
than my original proposal, where the same arguments were repeated on several
traces (plus a few more).

> 
>>> I don't see this here and besides, why in the hell would you need a
>>> trace event which only announces that the mechanism starts?? A common,
>>> run-of-the-mill printk is more than enough here.
>>
>> A daemon monitoring this trace may need to know when the trace mechanism
>> started, in order to what might be lost before the event init.
> 
> Yes, the trace has started when the daemon reads the first sample from the
> buffer, no need for explicitly letting us know it has.

Ok, I dropped the event class.

Patch enclosed.

Regards,
Mauro

-

events/hw_event: use a tracepoint-based Hardware Events Report Method (HERM)

From: Mauro Carvalho Chehab <mchehab@...hat.com>

Adds a trace class for handle hardware 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 hardware event subsystem, let's encapsulate the memory
error hardware events into a trace facility.

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@...hat.com>
Cc: Doug Thompson <norsk5@...oo.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Ingo Molnar <mingo@...hat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@...hat.com>

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..eff8266 100644
--- a/drivers/edac/edac_mc.c
+++ b/drivers/edac/edac_mc.c
@@ -33,6 +33,9 @@
 #include "edac_core.h"
 #include "edac_module.h"
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/hw_event.h>
+
 /* lock to memory controller's control array */
 static DEFINE_MUTEX(mem_ctls_mutex);
 static LIST_HEAD(mc_devices);
@@ -381,6 +384,7 @@ 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 +986,7 @@ 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 +1123,27 @@ 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_error(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/trace/events/hw_event.h b/include/trace/events/hw_event.h
new file mode 100644
index 0000000..234220a
--- /dev/null
+++ b/include/trace/events/hw_event.h
@@ -0,0 +1,77 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM hw_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 Anomaly Report Mecanism (HARM) events
+ *
+ * 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_error,
+
+	TP_PROTO(const unsigned int err_type,
+		 const unsigned int mc_index,
+		 const char *msg,
+		 const char *label,
+		 const char *location,
+		 const char *detail,
+		 const char *driver_detail),
+
+	TP_ARGS(err_type, mc_index, msg, label, location,
+		detail, driver_detail),
+
+	TP_STRUCT__entry(
+		__field(	unsigned int,	err_type		)
+		__field(	unsigned int,	mc_index		)
+		__string(	msg,		msg			)
+		__string(	label,		label			)
+		__string(	detail,		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, msg);
+		__assign_str(label, label);
+		__assign_str(location, location);
+		__assign_str(detail, detail);
+		__assign_str(driver_detail, driver_detail);
+	),
+
+	TP_printk(HW_ERR "mce#%d: %s error %s on memory stick \"%s\" (%s %s %s)",
+		  __entry->mc_index,
+		  (__entry->err_type == HW_EVENT_ERR_CORRECTED) ? "Corrected" :
+			((__entry->err_type == HW_EVENT_ERR_FATAL) ?
+			"Fatal" : "Uncorrected"),
+		  __get_str(msg),
+		  __get_str(label),
+		  __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>
--
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