[PATCH 2/5] dyndbg: add class_id field and query support
Jason Baron
jbaron at akamai.com
Fri Mar 11 19:06:13 UTC 2022
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 at rasmusvillemoes.dk>
> Signed-off-by: Jim Cromie <jim.cromie at 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;
> }
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