[Xenomai-core] [PATCH] separate queue debugging switch

[Xenomai-core] [PATCH] separate queue debugging switch

[Jan Kiszka]

[-- Attachment #1.1: Type: text/plain, Size: 364 bytes --]

Hi,

while XENO_OPT_DEBUG is generally a useful switch for tracing potential
issues in the core and the skins, it also introduces high latencies via
the queue debugging feature (due to checks iterating over whole queues).

This patch introduces separate control over queue debugging so that you
can have debug checks without too dramatic slowdowns.

Jan

[-- Attachment #1.2: DEBUG_QUEUES.patch --]
[-- Type: text/plain, Size: 2817 bytes --]

Index: ksrc/nucleus/Kconfig
===================================================================
--- ksrc/nucleus/Kconfig	(revision 564)
+++ ksrc/nucleus/Kconfig	(working copy)
@@ -87,6 +87,15 @@
 	Do not switch this option on unless you really know what you
 	are doing.
 
+config XENO_OPT_DEBUG_QUEUES
+	bool "Queue Debugging support"
+	depends on XENO_OPT_DEBUG
+	help
+	
+	This option activates debugging checks for all queueing
+	operations of the Xenomai core. It adds even more runtime
+	overhead then CONFIG_XENO_OPT_DEBUG, use with care.
+
 config XENO_OPT_WATCHDOG
 	bool "Watchdog support"
 	default n
Index: include/nucleus/queue.h
===================================================================
--- include/nucleus/queue.h	(revision 564)
+++ include/nucleus/queue.h	(working copy)
@@ -57,27 +57,27 @@
 
     xnholder_t head;
     int elems;
-#if defined(__KERNEL__) && defined(CONFIG_XENO_OPT_DEBUG) && defined(CONFIG_SMP)
+#if defined(__KERNEL__) && defined(CONFIG_XENO_OPT_DEBUG_QUEUES) && defined(CONFIG_SMP)
     xnlock_t lock;
-#endif /* __KERNEL__ && CONFIG_XENO_OPT_DEBUG && CONFIG_SMP */
+#endif /* __KERNEL__ && CONFIG_XENO_OPT_DEBUG_QUEUES && CONFIG_SMP */
 
 } xnqueue_t;
 
-#if defined(CONFIG_XENO_OPT_DEBUG) && defined(CONFIG_SMP)
+#if defined(CONFIG_XENO_OPT_DEBUG_QUEUES) && defined(CONFIG_SMP)
 #define DECLARE_XNQUEUE(q) xnqueue_t q = { { &(q).head, &(q).head }, 0, XNARCH_LOCK_UNLOCKED }
-#else /* !(CONFIG_XENO_OPT_DEBUG && CONFIG_SMP) */
+#else /* !(CONFIG_XENO_OPT_DEBUG_QUEUES && CONFIG_SMP) */
 #define DECLARE_XNQUEUE(q) xnqueue_t q = { { &(q).head, &(q).head }, 0 }
-#endif /* CONFIG_XENO_OPT_DEBUG && CONFIG_SMP */
+#endif /* CONFIG_XENO_OPT_DEBUG_QUEUES && CONFIG_SMP */
 
 static inline void initq (xnqueue_t *qslot) {
     inith(&qslot->head);
     qslot->elems = 0;
-#if defined(__KERNEL__) && defined(CONFIG_XENO_OPT_DEBUG) && defined(CONFIG_SMP)
+#if defined(__KERNEL__) && defined(CONFIG_XENO_OPT_DEBUG_QUEUES) && defined(CONFIG_SMP)
     xnlock_init(&qslot->lock);
-#endif /* __KERNEL__ && CONFIG_XENO_OPT_DEBUG && CONFIG_SMP */
+#endif /* __KERNEL__ && CONFIG_XENO_OPT_DEBUG_QUEUES && CONFIG_SMP */
 }
 
-#ifdef CONFIG_XENO_OPT_DEBUG
+#ifdef CONFIG_XENO_OPT_DEBUG_QUEUES
 
 #if defined(__KERNEL__) || defined(__XENO_UVM__) || defined(__XENO_SIM__)
 
@@ -172,7 +172,7 @@
    dth(__holder);				\
    --(__qslot)->elems; })
 
-#else /* !CONFIG_XENO_OPT_DEBUG */
+#else /* !CONFIG_XENO_OPT_DEBUG_QUEUES */
 
 static inline int insertq (xnqueue_t *qslot,
                            xnholder_t *head,
@@ -206,7 +206,7 @@
     return --qslot->elems;
 }
 
-#endif /* CONFIG_XENO_OPT_DEBUG */
+#endif /* CONFIG_XENO_OPT_DEBUG_QUEUES */
 
 static inline xnholder_t *getheadq (xnqueue_t *qslot)
 {

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 250 bytes --]

Re: [Xenomai-core] [PATCH] separate queue debugging switch

[Jan Kiszka]

[-- Attachment #1.1: Type: text/plain, Size: 448 bytes --]

Jan Kiszka wrote:
> Hi,
> 
> while XENO_OPT_DEBUG is generally a useful switch for tracing potential
> issues in the core and the skins, it also introduces high latencies via
> the queue debugging feature (due to checks iterating over whole queues).
> 
> This patch introduces separate control over queue debugging so that you
> can have debug checks without too dramatic slowdowns.
> 

And this revision also takes care of 2.4.

Jan

[-- Attachment #1.2: DEBUG_QUEUE-v2.patch --]
[-- Type: text/plain, Size: 3425 bytes --]

Index: ksrc/nucleus/Kconfig
===================================================================
--- ksrc/nucleus/Kconfig	(revision 564)
+++ ksrc/nucleus/Kconfig	(working copy)
@@ -87,6 +87,15 @@
 	Do not switch this option on unless you really know what you
 	are doing.
 
+config XENO_OPT_DEBUG_QUEUES
+	bool "Queue Debugging support"
+	depends on XENO_OPT_DEBUG
+	help
+	
+	This option activates debugging checks for all queueing
+	operations of the Xenomai core. It adds even more runtime
+	overhead then CONFIG_XENO_OPT_DEBUG, use with care.
+
 config XENO_OPT_WATCHDOG
 	bool "Watchdog support"
 	default n
Index: ksrc/nucleus/Config.in
===================================================================
--- ksrc/nucleus/Config.in	(revision 564)
+++ ksrc/nucleus/Config.in	(working copy)
@@ -18,6 +18,9 @@
 	bool 'Interrupt shield support' CONFIG_XENO_OPT_ISHIELD
 	bool 'Statistics collection' CONFIG_XENO_OPT_STATS
 	bool 'Debug support' CONFIG_XENO_OPT_DEBUG
+	if [ "$CONFIG_XENO_OPT_DEBUG" = "y" ]; then
+		bool 'Queue Debugging support' CONFIG_XENO_OPT_DEBUG_QUEUES
+	fi
 	bool 'Watchdog support' CONFIG_XENO_OPT_WATCHDOG
 
 	bool 'Enable periodic timer support' CONFIG_XENO_OPT_TIMING_PERIODIC
Index: include/nucleus/queue.h
===================================================================
--- include/nucleus/queue.h	(revision 564)
+++ include/nucleus/queue.h	(working copy)
@@ -57,27 +57,27 @@
 
     xnholder_t head;
     int elems;
-#if defined(__KERNEL__) && defined(CONFIG_XENO_OPT_DEBUG) && defined(CONFIG_SMP)
+#if defined(__KERNEL__) && defined(CONFIG_XENO_OPT_DEBUG_QUEUES) && defined(CONFIG_SMP)
     xnlock_t lock;
-#endif /* __KERNEL__ && CONFIG_XENO_OPT_DEBUG && CONFIG_SMP */
+#endif /* __KERNEL__ && CONFIG_XENO_OPT_DEBUG_QUEUES && CONFIG_SMP */
 
 } xnqueue_t;
 
-#if defined(CONFIG_XENO_OPT_DEBUG) && defined(CONFIG_SMP)
+#if defined(CONFIG_XENO_OPT_DEBUG_QUEUES) && defined(CONFIG_SMP)
 #define DECLARE_XNQUEUE(q) xnqueue_t q = { { &(q).head, &(q).head }, 0, XNARCH_LOCK_UNLOCKED }
-#else /* !(CONFIG_XENO_OPT_DEBUG && CONFIG_SMP) */
+#else /* !(CONFIG_XENO_OPT_DEBUG_QUEUES && CONFIG_SMP) */
 #define DECLARE_XNQUEUE(q) xnqueue_t q = { { &(q).head, &(q).head }, 0 }
-#endif /* CONFIG_XENO_OPT_DEBUG && CONFIG_SMP */
+#endif /* CONFIG_XENO_OPT_DEBUG_QUEUES && CONFIG_SMP */
 
 static inline void initq (xnqueue_t *qslot) {
     inith(&qslot->head);
     qslot->elems = 0;
-#if defined(__KERNEL__) && defined(CONFIG_XENO_OPT_DEBUG) && defined(CONFIG_SMP)
+#if defined(__KERNEL__) && defined(CONFIG_XENO_OPT_DEBUG_QUEUES) && defined(CONFIG_SMP)
     xnlock_init(&qslot->lock);
-#endif /* __KERNEL__ && CONFIG_XENO_OPT_DEBUG && CONFIG_SMP */
+#endif /* __KERNEL__ && CONFIG_XENO_OPT_DEBUG_QUEUES && CONFIG_SMP */
 }
 
-#ifdef CONFIG_XENO_OPT_DEBUG
+#ifdef CONFIG_XENO_OPT_DEBUG_QUEUES
 
 #if defined(__KERNEL__) || defined(__XENO_UVM__) || defined(__XENO_SIM__)
 
@@ -172,7 +172,7 @@
    dth(__holder);				\
    --(__qslot)->elems; })
 
-#else /* !CONFIG_XENO_OPT_DEBUG */
+#else /* !CONFIG_XENO_OPT_DEBUG_QUEUES */
 
 static inline int insertq (xnqueue_t *qslot,
                            xnholder_t *head,
@@ -206,7 +206,7 @@
     return --qslot->elems;
 }
 
-#endif /* CONFIG_XENO_OPT_DEBUG */
+#endif /* CONFIG_XENO_OPT_DEBUG_QUEUES */
 
 static inline xnholder_t *getheadq (xnqueue_t *qslot)
 {

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 250 bytes --]

Re: [Xenomai-core] [PATCH] separate queue debugging switch

[Gilles Chanteperdrix]

Jan Kiszka wrote:
 > Jan Kiszka wrote:
 > > Hi,
 > > 
 > > while XENO_OPT_DEBUG is generally a useful switch for tracing potential
 > > issues in the core and the skins, it also introduces high latencies via
 > > the queue debugging feature (due to checks iterating over whole queues).
 > > 
 > > This patch introduces separate control over queue debugging so that you
 > > can have debug checks without too dramatic slowdowns.
 > > 
 > 
 > And this revision also takes care of 2.4.

Applied, thanks.

-- 


					    Gilles Chanteperdrix.

Re: [Xenomai-core] [PATCH] separate queue debugging switch

[Philippe Gerum]

Jan Kiszka wrote:
> Hi,
> 
> while XENO_OPT_DEBUG is generally a useful switch for tracing potential
> issues in the core and the skins, it also introduces high latencies via
> the queue debugging feature (due to checks iterating over whole queues).
> 
> This patch introduces separate control over queue debugging so that you
> can have debug checks without too dramatic slowdowns.
> 

Maybe it's time to introduce debug levels, so that we could reuse them in order to
add more (selectable) debug instrumentation; queue debugging could then be given a
certain level (likely something like CONFIG_XENO_DEBUG_LEVEL=8712 for this 
one...), instead of going for a specific conditional each time we introduce new 
checks?

> Jan
> 
> 
> ------------------------------------------------------------------------
> 
> Index: ksrc/nucleus/Kconfig
> ===================================================================
> --- ksrc/nucleus/Kconfig	(revision 564)
> +++ ksrc/nucleus/Kconfig	(working copy)
> @@ -87,6 +87,15 @@
>  	Do not switch this option on unless you really know what you
>  	are doing.
>  
> +config XENO_OPT_DEBUG_QUEUES
> +	bool "Queue Debugging support"
> +	depends on XENO_OPT_DEBUG
> +	help
> +	
> +	This option activates debugging checks for all queueing
> +	operations of the Xenomai core. It adds even more runtime
> +	overhead then CONFIG_XENO_OPT_DEBUG, use with care.
> +
>  config XENO_OPT_WATCHDOG
>  	bool "Watchdog support"
>  	default n
> Index: include/nucleus/queue.h
> ===================================================================
> --- include/nucleus/queue.h	(revision 564)
> +++ include/nucleus/queue.h	(working copy)
> @@ -57,27 +57,27 @@
>  
>      xnholder_t head;
>      int elems;
> -#if defined(__KERNEL__) && defined(CONFIG_XENO_OPT_DEBUG) && defined(CONFIG_SMP)
> +#if defined(__KERNEL__) && defined(CONFIG_XENO_OPT_DEBUG_QUEUES) && defined(CONFIG_SMP)
>      xnlock_t lock;
> -#endif /* __KERNEL__ && CONFIG_XENO_OPT_DEBUG && CONFIG_SMP */
> +#endif /* __KERNEL__ && CONFIG_XENO_OPT_DEBUG_QUEUES && CONFIG_SMP */
>  
>  } xnqueue_t;
>  
> -#if defined(CONFIG_XENO_OPT_DEBUG) && defined(CONFIG_SMP)
> +#if defined(CONFIG_XENO_OPT_DEBUG_QUEUES) && defined(CONFIG_SMP)
>  #define DECLARE_XNQUEUE(q) xnqueue_t q = { { &(q).head, &(q).head }, 0, XNARCH_LOCK_UNLOCKED }
> -#else /* !(CONFIG_XENO_OPT_DEBUG && CONFIG_SMP) */
> +#else /* !(CONFIG_XENO_OPT_DEBUG_QUEUES && CONFIG_SMP) */
>  #define DECLARE_XNQUEUE(q) xnqueue_t q = { { &(q).head, &(q).head }, 0 }
> -#endif /* CONFIG_XENO_OPT_DEBUG && CONFIG_SMP */
> +#endif /* CONFIG_XENO_OPT_DEBUG_QUEUES && CONFIG_SMP */
>  
>  static inline void initq (xnqueue_t *qslot) {
>      inith(&qslot->head);
>      qslot->elems = 0;
> -#if defined(__KERNEL__) && defined(CONFIG_XENO_OPT_DEBUG) && defined(CONFIG_SMP)
> +#if defined(__KERNEL__) && defined(CONFIG_XENO_OPT_DEBUG_QUEUES) && defined(CONFIG_SMP)
>      xnlock_init(&qslot->lock);
> -#endif /* __KERNEL__ && CONFIG_XENO_OPT_DEBUG && CONFIG_SMP */
> +#endif /* __KERNEL__ && CONFIG_XENO_OPT_DEBUG_QUEUES && CONFIG_SMP */
>  }
>  
> -#ifdef CONFIG_XENO_OPT_DEBUG
> +#ifdef CONFIG_XENO_OPT_DEBUG_QUEUES
>  
>  #if defined(__KERNEL__) || defined(__XENO_UVM__) || defined(__XENO_SIM__)
>  
> @@ -172,7 +172,7 @@
>     dth(__holder);				\
>     --(__qslot)->elems; })
>  
> -#else /* !CONFIG_XENO_OPT_DEBUG */
> +#else /* !CONFIG_XENO_OPT_DEBUG_QUEUES */
>  
>  static inline int insertq (xnqueue_t *qslot,
>                             xnholder_t *head,
> @@ -206,7 +206,7 @@
>      return --qslot->elems;
>  }
>  
> -#endif /* CONFIG_XENO_OPT_DEBUG */
> +#endif /* CONFIG_XENO_OPT_DEBUG_QUEUES */
>  
>  static inline xnholder_t *getheadq (xnqueue_t *qslot)
>  {
> 
> 
> ------------------------------------------------------------------------
> 
> _______________________________________________
> Xenomai-core mailing list
> Xenomai-core@domain.hid
> https://mail.gna.org/listinfo/xenomai-core


-- 

Philippe.

Re: [Xenomai-core] [PATCH] separate queue debugging switch

[Jan Kiszka]

[-- Attachment #1: Type: text/plain, Size: 1455 bytes --]

Philippe Gerum wrote:
> Jan Kiszka wrote:
>> Hi,
>>
>> while XENO_OPT_DEBUG is generally a useful switch for tracing potential
>> issues in the core and the skins, it also introduces high latencies via
>> the queue debugging feature (due to checks iterating over whole queues).
>>
>> This patch introduces separate control over queue debugging so that you
>> can have debug checks without too dramatic slowdowns.
>>
> 
> Maybe it's time to introduce debug levels, so that we could reuse them
> in order to
> add more (selectable) debug instrumentation; queue debugging could then
> be given a
> certain level (likely something like CONFIG_XENO_DEBUG_LEVEL=8712 for
> this one...), instead of going for a specific conditional each time we
> introduce new checks?
> 

Hmm, this means someone have to define what should be printed at which
level - tend to be hard decisions... Often it is at least as much useful
to have debug groups so that specific parts can be excluded from
debugging. I'm pro such groups (one would be those queues e.g.) but
contra too many levels (2, at most 3).

At this chance, I would also suggest to introduce some ASSERT macro (per
group, per level). That could be used to instrument the core with
runtime checks. But it could also be quickly removed at compilation
time, reducing the code size (e.g. checks at the nucleus layer against
buggy skins or at RTDM layer against rough drivers).

Jan


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 250 bytes --]

Re: [Xenomai-core] [PATCH] separate queue debugging switch

[Philippe Gerum]

Jan Kiszka wrote:
> Philippe Gerum wrote:
> 
>>Jan Kiszka wrote:
>>
>>>Hi,
>>>
>>>while XENO_OPT_DEBUG is generally a useful switch for tracing potential
>>>issues in the core and the skins, it also introduces high latencies via
>>>the queue debugging feature (due to checks iterating over whole queues).
>>>
>>>This patch introduces separate control over queue debugging so that you
>>>can have debug checks without too dramatic slowdowns.
>>>
>>
>>Maybe it's time to introduce debug levels, so that we could reuse them
>>in order to
>>add more (selectable) debug instrumentation; queue debugging could then
>>be given a
>>certain level (likely something like CONFIG_XENO_DEBUG_LEVEL=8712 for
>>this one...), instead of going for a specific conditional each time we
>>introduce new checks?
>>
> 
> 
> Hmm, this means someone have to define what should be printed at which
> level - tend to be hard decisions... Often it is at least as much useful
> to have debug groups so that specific parts can be excluded from
> debugging. I'm pro such groups (one would be those queues e.g.) but
> contra too many levels (2, at most 3).
> 

Ack, selection by increasingly verbose/high-overhead groups is what I have in mind.

> At this chance, I would also suggest to introduce some ASSERT macro (per
> group, per level). That could be used to instrument the core with
> runtime checks. But it could also be quickly removed at compilation
> time, reducing the code size (e.g. checks at the nucleus layer against
> buggy skins or at RTDM layer against rough drivers).
>

I'm not opposed to that, if we keep the noise / signal ratio of those assertions 
at the reasonable low-level throughout the code, and don't use this to enforce 
silly parametrical checks.

> Jan
> 


-- 

Philippe.

Re: [Xenomai-core] [PATCH] separate queue debugging switch

[Jan Kiszka]

[-- Attachment #1: Type: text/plain, Size: 2924 bytes --]

Philippe Gerum wrote:
> Jan Kiszka wrote:
>> Philippe Gerum wrote:
>>
>>> Jan Kiszka wrote:
>>>
>>>> Hi,
>>>>
>>>> while XENO_OPT_DEBUG is generally a useful switch for tracing potential
>>>> issues in the core and the skins, it also introduces high latencies via
>>>> the queue debugging feature (due to checks iterating over whole
>>>> queues).
>>>>
>>>> This patch introduces separate control over queue debugging so that you
>>>> can have debug checks without too dramatic slowdowns.
>>>>
>>>
>>> Maybe it's time to introduce debug levels, so that we could reuse them
>>> in order to
>>> add more (selectable) debug instrumentation; queue debugging could then
>>> be given a
>>> certain level (likely something like CONFIG_XENO_DEBUG_LEVEL=8712 for
>>> this one...), instead of going for a specific conditional each time we
>>> introduce new checks?
>>>
>>
>>
>> Hmm, this means someone have to define what should be printed at which
>> level - tend to be hard decisions... Often it is at least as much useful
>> to have debug groups so that specific parts can be excluded from
>> debugging. I'm pro such groups (one would be those queues e.g.) but
>> contra too many levels (2, at most 3).
>>
> 
> Ack, selection by increasingly verbose/high-overhead groups is what I
> have in mind.
> 
>> At this chance, I would also suggest to introduce some ASSERT macro (per
>> group, per level). That could be used to instrument the core with
>> runtime checks. But it could also be quickly removed at compilation
>> time, reducing the code size (e.g. checks at the nucleus layer against
>> buggy skins or at RTDM layer against rough drivers).
>>
> 
> I'm not opposed to that, if we keep the noise / signal ratio of those
> assertions at the reasonable low-level throughout the code, and don't
> use this to enforce silly parametrical checks.
> 

Then let's discuss how to implement and control this. Say we have some
macros for marking code as "depends on debug group X":

#if XENO_DEBUG_GROUP(group)
code;
#endif /* XENO_DEBUG_GROUP(group) */

XENO_IF_DEBUG_GROUP(group, code);

(or do you prefere XNPOD_xxx?)

Additionally, we could introduce that assertion macro:

XENO_ASSERT(group, expression, failure_code);

But how to control the groups now? Via Kconfig bool options? And what
groups to define? Per subsytem? Or per disturbance level (latency
regression)? If we control the group selection via Kconfig, we could
define pseudo bool options like "All debug groups" or "Low-intrusive
debug groups" that select the fitting concrete groups.

Alternatively, we could make the group selection a runtime switch,
controlled via a global bitmask that can be modified through /proc e.g.
Only switching of CONFIG_XENO_OPT_DEBUG would then remove all debugging
code, otherwise the execution of the checks would depend on the current
bitmask content.

Jan


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 250 bytes --]

Re: [Xenomai-core] [PATCH] separate queue debugging switch

[Philippe Gerum]

Jan Kiszka wrote:
> Philippe Gerum wrote:
> 
>>Jan Kiszka wrote:
>>
>>>Philippe Gerum wrote:
>>>
>>>
>>>>Jan Kiszka wrote:
>>>>
>>>>
>>>>>Hi,
>>>>>
>>>>>while XENO_OPT_DEBUG is generally a useful switch for tracing potential
>>>>>issues in the core and the skins, it also introduces high latencies via
>>>>>the queue debugging feature (due to checks iterating over whole
>>>>>queues).
>>>>>
>>>>>This patch introduces separate control over queue debugging so that you
>>>>>can have debug checks without too dramatic slowdowns.
>>>>>
>>>>
>>>>Maybe it's time to introduce debug levels, so that we could reuse them
>>>>in order to
>>>>add more (selectable) debug instrumentation; queue debugging could then
>>>>be given a
>>>>certain level (likely something like CONFIG_XENO_DEBUG_LEVEL=8712 for
>>>>this one...), instead of going for a specific conditional each time we
>>>>introduce new checks?
>>>>
>>>
>>>
>>>Hmm, this means someone have to define what should be printed at which
>>>level - tend to be hard decisions... Often it is at least as much useful
>>>to have debug groups so that specific parts can be excluded from
>>>debugging. I'm pro such groups (one would be those queues e.g.) but
>>>contra too many levels (2, at most 3).
>>>
>>
>>Ack, selection by increasingly verbose/high-overhead groups is what I
>>have in mind.
>>
>>
>>>At this chance, I would also suggest to introduce some ASSERT macro (per
>>>group, per level). That could be used to instrument the core with
>>>runtime checks. But it could also be quickly removed at compilation
>>>time, reducing the code size (e.g. checks at the nucleus layer against
>>>buggy skins or at RTDM layer against rough drivers).
>>>
>>
>>I'm not opposed to that, if we keep the noise / signal ratio of those
>>assertions at the reasonable low-level throughout the code, and don't
>>use this to enforce silly parametrical checks.
>>
> 
> 
> Then let's discuss how to implement and control this. Say we have some
> macros for marking code as "depends on debug group X":
> 
> #if XENO_DEBUG_GROUP(group)
> code;
> #endif /* XENO_DEBUG_GROUP(group) */
> 
> XENO_IF_DEBUG_GROUP(group, code);
> 
> (or do you prefere XNPOD_xxx?)
> 

This debug code may span feature/component boundaries, so XENO_ is better.

> Additionally, we could introduce that assertion macro:
> 
> XENO_ASSERT(group, expression, failure_code);
> 
> But how to control the groups now? Via Kconfig bool options?

Yes, I think so. From some specialized Debug menu in the generic portion. We would 
need this to keep the (unused) debug code out of production systems.

  And what
> groups to define? Per subsytem? Or per disturbance level (latency
> regression)? If we control the group selection via Kconfig, we could
> define pseudo bool options like "All debug groups" or "Low-intrusive
> debug groups" that select the fitting concrete groups.
>

We won't be able to anticipate on each and every debug spots we might need in the 
future, and in any case, debug triggers may well span multiple sub-systems. I'd go 
for defining levels depending on the throroughness/complexity of their checks.

> Alternatively, we could make the group selection a runtime switch,
> controlled via a global bitmask that can be modified through /proc e.g.
> Only switching of CONFIG_XENO_OPT_DEBUG would then remove all debugging
> code, otherwise the execution of the checks would depend on the current
> bitmask content.

We could cumulate this with the static selection.

> 
> Jan
> 


-- 

Philippe.

Re: [Xenomai-core] [PATCH] separate queue debugging switch

[Jan Kiszka]

[-- Attachment #1: Type: text/plain, Size: 4290 bytes --]

Philippe Gerum wrote:
> Jan Kiszka wrote:
>> Philippe Gerum wrote:
>>
>>> Jan Kiszka wrote:
>>>
>>>> Philippe Gerum wrote:
>>>>
>>>>
>>>>> Jan Kiszka wrote:
>>>>>
>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> while XENO_OPT_DEBUG is generally a useful switch for tracing
>>>>>> potential
>>>>>> issues in the core and the skins, it also introduces high
>>>>>> latencies via
>>>>>> the queue debugging feature (due to checks iterating over whole
>>>>>> queues).
>>>>>>
>>>>>> This patch introduces separate control over queue debugging so
>>>>>> that you
>>>>>> can have debug checks without too dramatic slowdowns.
>>>>>>
>>>>>
>>>>> Maybe it's time to introduce debug levels, so that we could reuse them
>>>>> in order to
>>>>> add more (selectable) debug instrumentation; queue debugging could
>>>>> then
>>>>> be given a
>>>>> certain level (likely something like CONFIG_XENO_DEBUG_LEVEL=8712 for
>>>>> this one...), instead of going for a specific conditional each time we
>>>>> introduce new checks?
>>>>>
>>>>
>>>>
>>>> Hmm, this means someone have to define what should be printed at which
>>>> level - tend to be hard decisions... Often it is at least as much
>>>> useful
>>>> to have debug groups so that specific parts can be excluded from
>>>> debugging. I'm pro such groups (one would be those queues e.g.) but
>>>> contra too many levels (2, at most 3).
>>>>
>>>
>>> Ack, selection by increasingly verbose/high-overhead groups is what I
>>> have in mind.
>>>
>>>
>>>> At this chance, I would also suggest to introduce some ASSERT macro
>>>> (per
>>>> group, per level). That could be used to instrument the core with
>>>> runtime checks. But it could also be quickly removed at compilation
>>>> time, reducing the code size (e.g. checks at the nucleus layer against
>>>> buggy skins or at RTDM layer against rough drivers).
>>>>
>>>
>>> I'm not opposed to that, if we keep the noise / signal ratio of those
>>> assertions at the reasonable low-level throughout the code, and don't
>>> use this to enforce silly parametrical checks.
>>>
>>
>>
>> Then let's discuss how to implement and control this. Say we have some
>> macros for marking code as "depends on debug group X":
>>
>> #if XENO_DEBUG_GROUP(group)
>> code;
>> #endif /* XENO_DEBUG_GROUP(group) */
>>
>> XENO_IF_DEBUG_GROUP(group, code);
>>
>> (or do you prefere XNPOD_xxx?)
>>
> 
> This debug code may span feature/component boundaries, so XENO_ is better.
> 
>> Additionally, we could introduce that assertion macro:
>>
>> XENO_ASSERT(group, expression, failure_code);
>>
>> But how to control the groups now? Via Kconfig bool options?
> 
> Yes, I think so. From some specialized Debug menu in the generic
> portion. We would need this to keep the (unused) debug code out of
> production systems.
> 
>  And what
>> groups to define? Per subsytem? Or per disturbance level (latency
>> regression)? If we control the group selection via Kconfig, we could
>> define pseudo bool options like "All debug groups" or "Low-intrusive
>> debug groups" that select the fitting concrete groups.
>>
> 
> We won't be able to anticipate on each and every debug spots we might
> need in the future, and in any case, debug triggers may well span
> multiple sub-systems. I'd go for defining levels depending on the
> throroughness/complexity of their checks.
> 

To keep it simple:

XNDBG_LIGHT /* simple checks with low constant overhead */
XNDBG_HEAVY /* complex checks with high or unknown overhead */

Those two could become #defines and would have to be provide as first
argument to our debug macros.

Or we directly merge the attribute into the macro name:

XENO_DEBUG_LIGHT, XENO_IF_DEBUG_LIGHT(), XENO_ASSERT_LIGHT()
XENO_DEBUG_HEAVY, XENO_IF_DEBUG_HEAVY(), XENO_ASSERT_HEAVY()

>> Alternatively, we could make the group selection a runtime switch,
>> controlled via a global bitmask that can be modified through /proc e.g.
>> Only switching of CONFIG_XENO_OPT_DEBUG would then remove all debugging
>> code, otherwise the execution of the checks would depend on the current
>> bitmask content.
> 
> We could cumulate this with the static selection.
> 

Then this is also a perfect add-on - for later work. :)

Jan


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 252 bytes --]

Re: [Xenomai-core] [PATCH] separate queue debugging switch

[Philippe Gerum]

Jan Kiszka wrote:
> Philippe Gerum wrote:
> 
>>Jan Kiszka wrote:
>>
>>>Philippe Gerum wrote:
>>>
>>>
>>>>Jan Kiszka wrote:
>>>>
>>>>
>>>>>Philippe Gerum wrote:
>>>>>
>>>>>
>>>>>
>>>>>>Jan Kiszka wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>>Hi,
>>>>>>>
>>>>>>>while XENO_OPT_DEBUG is generally a useful switch for tracing
>>>>>>>potential
>>>>>>>issues in the core and the skins, it also introduces high
>>>>>>>latencies via
>>>>>>>the queue debugging feature (due to checks iterating over whole
>>>>>>>queues).
>>>>>>>
>>>>>>>This patch introduces separate control over queue debugging so
>>>>>>>that you
>>>>>>>can have debug checks without too dramatic slowdowns.
>>>>>>>
>>>>>>
>>>>>>Maybe it's time to introduce debug levels, so that we could reuse them
>>>>>>in order to
>>>>>>add more (selectable) debug instrumentation; queue debugging could
>>>>>>then
>>>>>>be given a
>>>>>>certain level (likely something like CONFIG_XENO_DEBUG_LEVEL=8712 for
>>>>>>this one...), instead of going for a specific conditional each time we
>>>>>>introduce new checks?
>>>>>>
>>>>>
>>>>>
>>>>>Hmm, this means someone have to define what should be printed at which
>>>>>level - tend to be hard decisions... Often it is at least as much
>>>>>useful
>>>>>to have debug groups so that specific parts can be excluded from
>>>>>debugging. I'm pro such groups (one would be those queues e.g.) but
>>>>>contra too many levels (2, at most 3).
>>>>>
>>>>
>>>>Ack, selection by increasingly verbose/high-overhead groups is what I
>>>>have in mind.
>>>>
>>>>
>>>>
>>>>>At this chance, I would also suggest to introduce some ASSERT macro
>>>>>(per
>>>>>group, per level). That could be used to instrument the core with
>>>>>runtime checks. But it could also be quickly removed at compilation
>>>>>time, reducing the code size (e.g. checks at the nucleus layer against
>>>>>buggy skins or at RTDM layer against rough drivers).
>>>>>
>>>>
>>>>I'm not opposed to that, if we keep the noise / signal ratio of those
>>>>assertions at the reasonable low-level throughout the code, and don't
>>>>use this to enforce silly parametrical checks.
>>>>
>>>
>>>
>>>Then let's discuss how to implement and control this. Say we have some
>>>macros for marking code as "depends on debug group X":
>>>
>>>#if XENO_DEBUG_GROUP(group)
>>>code;
>>>#endif /* XENO_DEBUG_GROUP(group) */
>>>
>>>XENO_IF_DEBUG_GROUP(group, code);
>>>
>>>(or do you prefere XNPOD_xxx?)
>>>
>>
>>This debug code may span feature/component boundaries, so XENO_ is better.
>>
>>
>>>Additionally, we could introduce that assertion macro:
>>>
>>>XENO_ASSERT(group, expression, failure_code);
>>>
>>>But how to control the groups now? Via Kconfig bool options?
>>
>>Yes, I think so. From some specialized Debug menu in the generic
>>portion. We would need this to keep the (unused) debug code out of
>>production systems.
>>
>> And what
>>
>>>groups to define? Per subsytem? Or per disturbance level (latency
>>>regression)? If we control the group selection via Kconfig, we could
>>>define pseudo bool options like "All debug groups" or "Low-intrusive
>>>debug groups" that select the fitting concrete groups.
>>>
>>
>>We won't be able to anticipate on each and every debug spots we might
>>need in the future, and in any case, debug triggers may well span
>>multiple sub-systems. I'd go for defining levels depending on the
>>throroughness/complexity of their checks.
>>
> 
> 
> To keep it simple:
> 
> XNDBG_LIGHT /* simple checks with low constant overhead */
> XNDBG_HEAVY /* complex checks with high or unknown overhead */
> 
> Those two could become #defines and would have to be provide as first
> argument to our debug macros.
> 
> Or we directly merge the attribute into the macro name:
> 
> XENO_DEBUG_LIGHT, XENO_IF_DEBUG_LIGHT(), XENO_ASSERT_LIGHT()
> XENO_DEBUG_HEAVY, XENO_IF_DEBUG_HEAVY(), XENO_ASSERT_HEAVY()
>

There's no need to limit the number of debug levels, since defining what goes into
each of them is a matter of developer's appreciation, wrt induced overhead, and/or 
debug thoroughness. IOW, let's not impose any policy here. To keep things really 
simple, we'd also need to decouple the assertion mechanism from the debug 
thoroughness, E.g.

#if XENO_DEBUG_LEVEL > 0
#define XENO_ASSERT(cond,action,fmt,args...)  do { \
if (unlikely((cond) != 0)) \
     (action)(fmt , ##args); \
} while(0)
#else  /* DEBUG OFF */
#define XENO_ASSERT(cond,action,fmt,args...) do { } while(0)
#endif /* DEBUG ON */

#define XENO_BUGON(cond)  \
XENO_ASSERT(cond,xnpod_fatal,"assertion failed at %s:%d",__FILE__,__LINE__)

This way, we could reserve level #1 (and above by extension) to activate all 
assertions; if people need to even control the thoroughness of assertions, they 
could just resort to implementing the assertion code in a separate debug function 
testing for particular debug levels, then calling this routine as XENO_BUGON's 
"cond" argument. Keeping level #0 free from assertions would be nice for 
production systems. E.g.

#if XENO_DEBUG_LEVEL > 2
	check_all_nucleus_queues();
#endif
...
	XENO_BUGON(I_am_so_sorry);

and so on.

Setting a value for XENO_DEBUG_LEVEL would be trivial using Kconfig. Dynamic 
setting of the debug level through /proc could be obtained by forcing 
XENO_DEBUG_LEVEL to MAX_INT (i.e. when dynamic debug levels are selected from 
Kconfig), and testing some addition global variable within the debug code to 
filter out unwanted checks.

> 
>>>Alternatively, we could make the group selection a runtime switch,
>>>controlled via a global bitmask that can be modified through /proc e.g.
>>>Only switching of CONFIG_XENO_OPT_DEBUG would then remove all debugging
>>>code, otherwise the execution of the checks would depend on the current
>>>bitmask content.
>>
>>We could cumulate this with the static selection.
>>
> 
> 
> Then this is also a perfect add-on - for later work. :)
> 
> Jan
> 


-- 

Philippe.