Re: [PATCH 2/5] dyndbg: add class_id field and query support

On 3/10/22 23:47, Jim Cromie wrote:

DRM defines/uses 10 enum drm_debug_category's to create exclusive classes of debug messages. To support this directly in dynamic-debug, add the following:

• struct _ddebug.class_id:4 - 4 bits is enough
• define _DPRINTK_SITE_UNCLASSED 15 - see below

and the query support:

• struct _ddebug_query.class_id
• ddebug_parse_query - looks for "class" keyword, then calls..
• parse_class - accepts uint: 0-15, sets query.class_id and marker
• vpr_info_dq - displays new field
• ddebug_proc_show - append column with "cls:%d" if !UNCLASSED

With the patch, one can enable current/unclassed callsites by:

#> echo drm class 15 +p > /proc/dynamic_debug/control

To me, this is hard to read, what the heck is '15'? I have to go look it up in the control file and it's not descriptive. I think that using classes/categories makes sense but I'm wondering if it can be a bit more user friendly? Perhaps, we can pass an array of strings that is indexed by the class id to each pr_debug() site that wants to use class. So something like:

enum levels { LOW, MEDIUM, HIGH };

static const char * const level_to_strings[] = { [LOW] = "low", [MEDIUM] = "medium", [HIGH] = "high", };

And then you'd have a wrapper macros in your driver:

#define module_foo_pr_debug_class(level, fmt, args...) pr_debug_class(level, level_to_strings, fmt, args);

Such that call sites look like:

module_foo_pr_debug_class(LOW, fmt, args...);

Such that you're not always passing the strings array around. Now, this does mean another pointer for struct _ddebug and most wouldn't have it. Maybe we could just add another linker section for these so as to save space.

parse_class() accepts 0 .. _DPRINTK_SITE_UNCLASSED, which allows the

...

control interface to explicitly manipulate unclassed callsites.

After parsing keywords, ddebug_parse_query() sets .class_id=15, iff it wasnt explicitly set. This allows future classed/categorized callsites to be untouched by legacy (class unaware) queries.

DEFINE_DYNAMIC_DEBUG_METADATA gets _CLS(cls,) suffix and arg, and initializes the new .class_id=cls field. The old name gets the default.

Then, these _CLS(cls,...) modifications are repeated up through the stack of *dynamic_func_call* macros that use the METADATA initializer, so as to actually supply the category into it.

NOTES:

_DPRINTK_SITE_UNCLASSED: this symbol is used to initialize all existing/unclassed pr-debug callsites. Normally, the default would be zero, but DRM_UT_CORE "uses" that value, in the sense that 0 is exposed as a bit position in drm.debug. Using 15 allows identity mapping from category to class, avoiding fiddly offsets.

Default .class_id = 15 means that ``echo +p > control`` no longer toggles ALL the callsites, only the unclassed ones. This was only useful for static-branch toggle load testing anyway.

I think that # echo +p > control should continue to work as is, why should the introduction of classes change that ?

RFC:

The new _CLS macro flavor gets a warning from DRM/dri-devel's CI, but not from checkpatch (on this subject).

a8f6c71f283e dyndbg: add class_id field and query support -:141: CHECK:MACRO_ARG_REUSE: Macro argument reuse 'id' - possible side-effects? +#define __dynamic_func_call_cls(id, cls, fmt, func, ...) do { \

• DEFINE_DYNAMIC_DEBUG_METADATA_CLS(id, cls, fmt); \
• if (DYNAMIC_DEBUG_BRANCH(id)) \

• func(&id, ##__VA_ARGS__);			\
  

} while (0)

I couldn't fix it with a ``typeof(id) _id = id`` construct. I haven't seen the warning myself, on the _CLS extended macro, nor the original.

CC: Rasmus Villemoes linux@rasmusvillemoes.dk Signed-off-by: Jim Cromie jim.cromie@gmail.com

---

.../admin-guide/dynamic-debug-howto.rst | 7 +++ include/linux/dynamic_debug.h | 54 ++++++++++++++----- lib/dynamic_debug.c | 48 ++++++++++++++--- 3 files changed, 88 insertions(+), 21 deletions(-)

diff --git a/Documentation/admin-guide/dynamic-debug-howto.rst b/Documentation/admin-guide/dynamic-debug-howto.rst index a89cfa083155..8ef8d7dcd140 100644 --- a/Documentation/admin-guide/dynamic-debug-howto.rst +++ b/Documentation/admin-guide/dynamic-debug-howto.rst @@ -35,6 +35,7 @@ Dynamic debug has even more useful features: - line number (including ranges of line numbers) - module name - format string

• • class number:0-15
  • Provides a debugfs control file: ``<debugfs>/dynamic_debug/control``

  which can be read to display the complete list of known debug

@@ -143,6 +144,7 @@ against. Possible keywords are::: 'module' string | 'format' string | 'line' line-range

•  'class' integer:[0-15]
  
  

  line-range ::= lineno | '-'lineno |

@@ -217,6 +219,11 @@ line line -1605 // the 1605 lines from line 1 to line 1605 line 1600- // all lines from line 1600 to the end of the file

+class

• This expects a single integer in range: 0-15.
• 15 is used/reserved for existing/unclassed callsites,
• and is defaulted in unless specified to >control

The flags specification comprises a change operation followed by one or more flag characters. The change operation is one of the characters:: diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h index dce631e678dd..d4b48f3cc6e8 100644 --- a/include/linux/dynamic_debug.h +++ b/include/linux/dynamic_debug.h @@ -6,6 +6,8 @@ #include <linux/jump_label.h> #endif

+#include <linux/build_bug.h>

/*

• An instance of this structure is created in a special
• ELF section at every dynamic debug callsite. At runtime,

@@ -21,6 +23,9 @@ struct _ddebug { const char *filename; const char *format; unsigned int lineno:18; +#define CLS_BITS 4

• unsigned int class_id:CLS_BITS;

+#define _DPRINTK_SITE_UNCLASSED ((1 << CLS_BITS) - 1) /* * The flags field controls the behaviour at the callsite. * The bits here are changed dynamically when the user @@ -87,7 +92,7 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor, const struct ib_device *ibdev, const char *fmt, ...);

-#define DEFINE_DYNAMIC_DEBUG_METADATA(name, fmt) \ +#define DEFINE_DYNAMIC_DEBUG_METADATA_CLS(name, cls, fmt) \ static struct _ddebug __aligned(8) \ __section("__dyndbg") name = { \ .modname = KBUILD_MODNAME, \ @@ -96,8 +101,14 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor, .format = (fmt), \ .lineno = __LINE__, \ .flags = _DPRINTK_FLAGS_DEFAULT, \

• .class_id = cls,				\
  

  _DPRINTK_KEY_INIT \

• }

• }; \
• BUILD_BUG_ON_MSG(cls > _DPRINTK_SITE_UNCLASSED, \

• 	 "classid value overflow")
  

+#define DEFINE_DYNAMIC_DEBUG_METADATA(name, fmt) \

• DEFINE_DYNAMIC_DEBUG_METADATA_CLS(name, _DPRINTK_SITE_UNCLASSED, fmt)

#ifdef CONFIG_JUMP_LABEL

@@ -128,18 +139,26 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor,

#endif /* CONFIG_JUMP_LABEL */

-#define __dynamic_func_call(id, fmt, func, ...) do { \

• DEFINE_DYNAMIC_DEBUG_METADATA(id, fmt); \
• if (DYNAMIC_DEBUG_BRANCH(id)) \

• func(&id, ##__VA_ARGS__);		\
  

+#define __dynamic_func_call_cls(id, cls, fmt, func, ...) do { \

• DEFINE_DYNAMIC_DEBUG_METADATA_CLS(id, cls, fmt); \
• if (DYNAMIC_DEBUG_BRANCH(id)) \

• func(&id, ##__VA_ARGS__);			\
  

} while (0)

-#define __dynamic_func_call_no_desc(id, fmt, func, ...) do { \

• DEFINE_DYNAMIC_DEBUG_METADATA(id, fmt); \
• if (DYNAMIC_DEBUG_BRANCH(id)) \

• func(__VA_ARGS__);				\
  

+#define __dynamic_func_call_no_desc_cls(id, cls, fmt, func, ...) do { \

• DEFINE_DYNAMIC_DEBUG_METADATA_CLS(id, cls, fmt); \
• if (DYNAMIC_DEBUG_BRANCH(id)) \

• func(__VA_ARGS__);					\
  

} while (0)

+#define __dynamic_func_call(id, fmt, func, ...) \

• __dynamic_func_call_cls(id, _DPRINTK_SITE_UNCLASSED, \

• 		fmt, func, ##__VA_ARGS__)
  

+#define __dynamic_func_call_no_desc(id, fmt, func, ...) \

• __dynamic_func_call_no_desc_cls(id, _DPRINTK_SITE_UNCLASSED, \

• 			fmt, func, ##__VA_ARGS__)
  

/*

• "Factory macro" for generating a call to func, guarded by a
• DYNAMIC_DEBUG_BRANCH. The dynamic debug descriptor will be

@@ -148,15 +167,24 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor,

• the varargs. Note that fmt is repeated in invocations of this
• macro.

*/ +#define _dynamic_func_call_cls(cls, fmt, func, ...) \

• __dynamic_func_call_cls(__UNIQUE_ID(ddebug), cls, fmt, func, ##__VA_ARGS__)

#define _dynamic_func_call(fmt, func, ...) \

• __dynamic_func_call(__UNIQUE_ID(ddebug), fmt, func, ##__VA_ARGS__)

• _dynamic_func_call_cls(_DPRINTK_SITE_UNCLASSED, fmt, func, ##__VA_ARGS__)

/*

• A variant that does the same, except that the descriptor is not
• passed as the first argument to the function; it is only called
• with precisely the macro's varargs.

*/ -#define _dynamic_func_call_no_desc(fmt, func, ...) \

• __dynamic_func_call_no_desc(__UNIQUE_ID(ddebug), fmt, func, ##__VA_ARGS__)

+#define _dynamic_func_call_no_desc_cls(fmt, cat, func, ...) \

• __dynamic_func_call_no_desc_cls(__UNIQUE_ID(ddebug), cat, \

• 			fmt, func, ##__VA_ARGS__)
  

+#define _dynamic_func_call_no_desc(fmt, func, ...) \

• __dynamic_func_call_no_desc_cls(__UNIQUE_ID(ddebug), \

• 			_DPRINTK_SITE_UNCLASSED,	\
  

• 			fmt, func, ##__VA_ARGS__)
  
  

#define dynamic_pr_debug(fmt, ...) \ _dynamic_func_call(fmt, __dynamic_pr_debug, \ diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c index a56c1286ffa4..ee2129becacc 100644 --- a/lib/dynamic_debug.c +++ b/lib/dynamic_debug.c @@ -55,6 +55,8 @@ struct ddebug_query { const char *function; const char *format; unsigned int first_lineno, last_lineno;

• unsigned int class_id;
• unsigned int class_marked:1;

};

struct ddebug_iter { @@ -134,13 +136,13 @@ static void vpr_info_dq(const struct ddebug_query *query, const char *msg) fmtlen--; }

• v3pr_info("%s: func="%s" file="%s" module="%s" format="%.*s" lineno=%u-%u\n",

•  msg,
  

•  query->function ?: "",
  

•  query->filename ?: "",
  

•  query->module ?: "",
  

•  fmtlen, query->format ?: "",
  

•  query->first_lineno, query->last_lineno);
  

• v3pr_info("%s: func="%s" file="%s" module="%s" format="%.*s" lineno=%u-%u class=%u\n",

•   msg,
  

•   query->function ?: "",
  

•   query->filename ?: "",
  

•   query->module ?: "",
  

•   fmtlen, query->format ?: "",
  

•   query->first_lineno, query->last_lineno, query->class_id);
  

}

/* @@ -170,6 +172,10 @@ static int ddebug_change(const struct ddebug_query *query, for (i = 0; i < dt->num_ddebugs; i++) { struct _ddebug *dp = &dt->ddebugs[i];

• 	/* match against the class_id, either given or default */
  

• 	if (query->class_id != dp->class_id)
  

• 		continue;
  

Could that instead be:

if (query->class_id != _DPRINTK_SITE_UNCLASSED && query->class_id != dp->class_id) continue;

That way by default we fall through and enable callsites for queries that do not have the 'class' keyboard specified. I think I would also disallow setting _DPRINTK_SITE_UNCLASSED explicitly since it would now mean 'class *', and what if we expand class_id size to greater than 15 at some point?

	/* match against the source filename */
	if (query->filename &&
	    !match_wildcard(query->filename, dp->filename) &&

@@ -308,6 +314,21 @@ static inline int parse_lineno(const char *str, unsigned int *val) return 0; }

+static inline int parse_class(struct ddebug_query *query, const char *str) +{

• int rc;
• unsigned int val;
• rc = kstrtouint(str, 10, &val);
• if (rc < 0 || val > _DPRINTK_SITE_UNCLASSED) {

• pr_err("expecting class:[0-%d], not %s\n", _DPRINTK_SITE_UNCLASSED, str);
  

• return -EINVAL;
  

• }
• query->class_id = val;
• query->class_marked = 1;
• return 0;

+}

static int parse_linerange(struct ddebug_query *query, const char *first) { char *last = strchr(first, '-'); @@ -421,6 +442,9 @@ static int ddebug_parse_query(char *words[], int nwords, } else if (!strcmp(keyword, "line")) { if (parse_linerange(query, arg)) return -EINVAL;

• } else if (!strcmp(keyword, "class")) {
  

• 	if (parse_class(query, arg))
  

• 		return -EINVAL;
  

  } else { pr_err("unknown keyword "%s"\n", keyword); return -EINVAL;

@@ -428,6 +452,10 @@ static int ddebug_parse_query(char *words[], int nwords, if (rc) return rc; }

• /* post-validate the query, set default */
• if (!query->class_marked)

• query->class_id = _DPRINTK_SITE_UNCLASSED;
  

• vpr_info_dq(query, "parsed"); return 0;

} @@ -900,7 +928,11 @@ static int ddebug_proc_show(struct seq_file *m, void *p) iter->table->mod_name, dp->function, ddebug_describe_flags(dp->flags, &flags)); seq_escape(m, dp->format, "\t\r\n"");

• seq_puts(m, ""\n");

• seq_puts(m, """);

• if (dp->class_id != _DPRINTK_SITE_UNCLASSED)

• seq_printf(m, " cls:%u", dp->class_id);
  

• seq_puts(m, "\n");

  return 0;

}