linux-kernel - [PATCH v2 14/59] dyndbg: split _emit_lookup() out of dynamic_emit

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Message-ID: <20250320185238.447458-15-jim.cromie@gmail.com>
Date: Thu, 20 Mar 2025 12:51:52 -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 14/59] dyndbg: split _emit_lookup() out of dynamic_emit_prefix()

Split dynamic_emit_prefix() to separate out _INCL_LOOKUPs:

1. keep dynamic_emit_prefix() static inline
   check _INCL_ANY flags before calling 2

2. __dynamic_emit_prefix()
   prints [TID] or <intr> and trailing space if +t flag
   check _INCL_LOOKUP flags before calling 3

3. __dynamic_emit_lookup()
   prints ONLY module, function, src, line, and trailing space
   TID isn't "callsite" specific info.
   result is "cacheable"

Notes:

2,3 are gated, only called when theyve something to emit, so they just
add trailing space.  This obsoletes the pos_after_tid var and logic.

__dynamic_emit_lookup() adds line too, so the result is "whole".
While this would enlarge a naive cache vs add-line-after-caching, we
dont even have a naive one yet.

And some clever indexing on store() might be able to fold the flags
setting in, such that the prefix stored with +mf flags only (-l),
could be returned for all pr_debugs in that function which also had
+mf flags. While still supporting +mfsl prefixes (with cache
expansion) as they're used.

Signed-off-by: Jim Cromie <jim.cromie@...il.com>
---
 lib/dynamic_debug.c | 40 +++++++++++++++++++++++++---------------
 1 file changed, 25 insertions(+), 15 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 663c125006d0..f7ec2365ab40 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -850,19 +850,8 @@ static int remaining(int wrote)
 	return 0;
 }
 
-static char *__dynamic_emit_prefix(const struct _ddebug *desc, char *buf)
+static int __dynamic_emit_lookup(const struct _ddebug *desc, char *buf, int pos)
 {
-	int pos_after_tid;
-	int pos = 0;
-
-	if (desc->flags & _DPRINTK_FLAGS_INCL_TID) {
-		if (in_interrupt())
-			pos += snprintf(buf + pos, remaining(pos), "<intr> ");
-		else
-			pos += snprintf(buf + pos, remaining(pos), "[%d] ",
-					task_pid_vnr(current));
-	}
-	pos_after_tid = pos;
 	if (desc->flags & _DPRINTK_FLAGS_INCL_MODNAME)
 		pos += snprintf(buf + pos, remaining(pos), "%s:",
 				desc->modname);
@@ -875,8 +864,29 @@ static char *__dynamic_emit_prefix(const struct _ddebug *desc, char *buf)
 	if (desc->flags & _DPRINTK_FLAGS_INCL_LINENO)
 		pos += snprintf(buf + pos, remaining(pos), "%d:",
 				desc->lineno);
-	if (pos - pos_after_tid)
-		pos += snprintf(buf + pos, remaining(pos), " ");
+
+	/* cuz LOOKUP, we've emitted, so add trailing space if room */
+	if (remaining(pos))
+		buf[pos++] = ' ';
+
+	return pos;
+}
+
+static char *__dynamic_emit_prefix(struct _ddebug *desc, char *buf)
+{
+	int pos = 0;
+
+	if (desc->flags & _DPRINTK_FLAGS_INCL_TID) {
+		if (in_interrupt())
+			pos += snprintf(buf + pos, remaining(pos), "<intr> ");
+		else
+			pos += snprintf(buf + pos, remaining(pos), "[%d] ",
+					task_pid_vnr(current));
+	}
+
+	if (unlikely(desc->flags & _DPRINTK_FLAGS_INCL_LOOKUP))
+		pos += __dynamic_emit_lookup(desc, buf, pos);
+
 	if (pos >= PREFIX_SIZE)
 		buf[PREFIX_SIZE - 1] = '\0';
 
@@ -885,7 +895,7 @@ static char *__dynamic_emit_prefix(const struct _ddebug *desc, char *buf)
 
 static inline char *dynamic_emit_prefix(struct _ddebug *desc, char *buf)
 {
-	if (unlikely(desc->flags & _DPRINTK_FLAGS_INCL_ANY))
+	if (desc->flags & _DPRINTK_FLAGS_INCL_ANY)
 		return __dynamic_emit_prefix(desc, buf);
 	return buf;
 }
-- 
2.49.0