linux-kernel - [PATCH v2 13/59] dyndbg: add 2 new _DPRINTK_FLAGS_: INCL_LOOKUP, PREFIX

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Message-ID: <20250320185238.447458-14-jim.cromie@gmail.com>
Date: Thu, 20 Mar 2025 12:51:51 -0600
From: Jim Cromie <jim.cromie@...il.com>
To: linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	amd-gfx@...ts.freedesktop.org,
	intel-gvt-dev@...ts.freedesktop.org,
	intel-gfx@...ts.freedesktop.org,
	intel-gfx-trybot@...ts.freedesktop.org
Cc: jbaron@...mai.com,
	gregkh@...uxfoundation.org,
	ukaszb@...omium.org,
	louis.chauvet@...tlin.com,
	daniel.vetter@...ll.ch,
	tvrtko.ursulin@...ux.intel.com,
	jani.nikula@...el.com,
	ville.syrjala@...ux.intel.com,
	Jim Cromie <jim.cromie@...il.com>
Subject: [PATCH v2 13/59] dyndbg: add 2 new _DPRINTK_FLAGS_: INCL_LOOKUP, PREFIX_CACHED

Add _INCL_LOOKUP condition to separate +mfsl flags from +t, allowing
(after refactoring) to avoid a needless call-return.

Add a PREFIX_CACHED bit to remember that a pr-debug callsite is:

- enabled, with +p
- wants a dynamic-prefix, with _INCL_LOOKUP
- was previously called
- was thus saved in the prefix cache. NOT YET.

This allows (later) to cache part/all of the dynamic-prefix for each
pr_debug that gets called.

NOTES:

dyndbg's dynamic prefixing can get expensive; each enabled callsite's
prefix is sprintf'd into stack-mem, every time a pr_debug is called.

A cache would help, if callsites mark _DPRINTK_FLAGS_PREFIX_CACHED
after saving the prefix string.  But not yet.

-t  thread-id. not part of the "callsite" info, derived from current.
    doesn't belong in the cache. it would be wrong.
    can be done in outer: dynamic_emit_prefix()

-mfsl  module, function, source-file, line
    we cache these, composed into a sub-string.
    they are "lookups", currently to descriptor fields,.
    could be accessor macros to "compressed" tables.

All enabled together, they compose a prefix string like:

  # outer   -----inner-------------------
  "[tid] module:function:sourcfile:line: "

So this patch extracts _DPRINTK_FLAGS_INCL_LOOKUP macro out of
_DPRINTK_FLAGS_INCL_ANY macro, then redefs latter.

Next re-refactor dynamic_emit_prefix inner/outer fns accordingly.

Signed-off-by: Jim Cromie <jim.cromie@...il.com>
---
 include/linux/dynamic_debug.h | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index c388ab05a6e1..82eabaa6e827 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -38,11 +38,13 @@ struct _ddebug {
 #define _DPRINTK_FLAGS_INCL_LINENO	(1<<3)
 #define _DPRINTK_FLAGS_INCL_TID		(1<<4)
 #define _DPRINTK_FLAGS_INCL_SOURCENAME	(1<<5)
+#define _DPRINTK_FLAGS_PREFIX_CACHED	(1<<7)
 
-#define _DPRINTK_FLAGS_INCL_ANY		\
-	(_DPRINTK_FLAGS_INCL_MODNAME | _DPRINTK_FLAGS_INCL_FUNCNAME |\
-	 _DPRINTK_FLAGS_INCL_LINENO  | _DPRINTK_FLAGS_INCL_TID |\
-	 _DPRINTK_FLAGS_INCL_SOURCENAME)
+#define _DPRINTK_FLAGS_INCL_LOOKUP					\
+	(_DPRINTK_FLAGS_INCL_MODNAME | _DPRINTK_FLAGS_INCL_FUNCNAME |	\
+	 _DPRINTK_FLAGS_INCL_SOURCENAME | _DPRINTK_FLAGS_INCL_LINENO)
+#define _DPRINTK_FLAGS_INCL_ANY						\
+	(_DPRINTK_FLAGS_INCL_TID | _DPRINTK_FLAGS_INCL_LOOKUP)
 
 #if defined DEBUG
 #define _DPRINTK_FLAGS_DEFAULT _DPRINTK_FLAGS_PRINT
-- 
2.49.0