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From:   Jim Cromie <jim.cromie@gmail.com>
To:     jbaron@akamai.com, gregkh@linuxfoundation.org,
        linux-kernel@vger.kernel.org
Cc:     Jim Cromie <jim.cromie@gmail.com>
Subject: [RFC PATCH v6 34/34] dyndbg: prototype print-once and print-ratelimited RFC
Date:   Sat, 29 May 2021 14:00:29 -0600
Message-Id: <20210529200029.205306-35-jim.cromie@gmail.com>
In-Reply-To: <20210529200029.205306-1-jim.cromie@gmail.com>
References: <20210529200029.205306-1-jim.cromie@gmail.com>
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Expand ddebug.flags to 11 bits, and define new flags to support
pr_debug_once() and pr_debug_ratelimited() semantics:

  echo module main +o > control		# init/main runs once anyway
  echo module foo +r > control		# turn on ratelimiting
  echo module foo +g > control		# turn on group flag

Test these conditions in new is_onced_or_ratelimited(),
and call it from __dynamic_pr_debug and others.

print-once: can be done with just 2 bits in flags;

.o _DPRINTK_FLAGS_ONCE     enables state test and set
.P _DPRINTK_FLAGS_PRINTED  state bit

Just adding the flags lets the existing code operate them.
We will need new code to enforce constraints on flag combos;
'+ro' is nonsense, but this can wait, or can take a new meaning.

is_onced_or_ratelimited() should be correct for +o,
and should be testable now. tbd.

rate-limiting:
.  for now, reserve the flag only !
.r _DPRINTK_FLAGS_RATELIMITED	- track & limit prdbgs callrate

Intention is to wait til a prdebug is called, and if RATELIMITED is
set, THEN lookup a RateLimitState (RL) for it.  If found, bump its
state and return true/false, otherwise create one, initialize it and
return false.

That lookup is basically a hash, with 2 part key:
. &builtin-vector-base OR &module
  or the hash(s) could hang off the header struct
. ._back OR ._map
  chosen by _DPRINTK_FLAGS_GROUPED
  choice dictates per-site OR sharing across function

heres what happens:
- header fail seen before, time to dig more

dyndbg: get: header fail on 100-3231
dyndbg: changed drivers/gpu/drm/i915/gvt/mmio_context.c:3231 [i915]restore_context_mmio_for_inhibit =prg
dyndbg: get: header fail on 101-1412
dyndbg: changed drivers/gpu/drm/i915/gvt/cmd_parser.c:1412 [i915]init_cmd_table =prg
dyndbg: get: header fail on 102-1409
dyndbg: changed drivers/gpu/drm/i915/gvt/cmd_parser.c:1409 [i915]gen8_check_mi_display_flip =prg
dyndbg: get: header fail on 103-761
dyndbg: changed drivers/gpu/drm/i915/gvt/cmd_parser.c:761 [i915]gen8_check_mi_display_flip =prg
dyndbg: get: header fail on 104-760
dyndbg: changed drivers/gpu/drm/i915/gvt/cmd_parser.c:760 [i915]parser_exec_state_dump =prg
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
 include/linux/dynamic_debug.h | 10 ++++++---
 lib/dynamic_debug.c           | 42 ++++++++++++++++++++++++++++++++++-
 2 files changed, 48 insertions(+), 4 deletions(-)

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index fe70dda704d2..300fd0eed66f 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -64,18 +64,22 @@ struct _ddebug {
 #define _DPRINTK_FLAGS_INCL_FUNCNAME	(1<<2)
 #define _DPRINTK_FLAGS_INCL_LINENO	(1<<3)
 #define _DPRINTK_FLAGS_INCL_TID		(1<<4)
-#define _DPRINTK_FLAGS_DELETE_SITE	(1<<7) /* drop site info to save ram */
-
 #define _DPRINTK_FLAGS_INCL_ANY		\
 	(_DPRINTK_FLAGS_INCL_MODNAME | _DPRINTK_FLAGS_INCL_FUNCNAME |\
 	 _DPRINTK_FLAGS_INCL_LINENO  | _DPRINTK_FLAGS_INCL_TID)
 
+#define _DPRINTK_FLAGS_ONCE		(1<<5) /* print once flag */
+#define _DPRINTK_FLAGS_PRINTED		(1<<6) /* print once state */
+#define _DPRINTK_FLAGS_RATELIMITED	(1<<7)
+#define _DPRINTK_FLAGS_GROUPED		(1<<8) /* manipulate as a group */
+#define _DPRINTK_FLAGS_DELETE_SITE	(1<<9) /* drop site info to save ram */
+
 #if defined DEBUG
 #define _DPRINTK_FLAGS_DEFAULT _DPRINTK_FLAGS_PRINT
 #else
 #define _DPRINTK_FLAGS_DEFAULT 0
 #endif
-	unsigned int flags:8;
+	unsigned int flags:11;
 
 #ifdef CONFIG_JUMP_LABEL
 	union {
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 66b48f1cb2d0..a81461b58f6e 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -86,13 +86,17 @@ static inline const char *trim_prefix(const char *path)
 	return path + skip;
 }
 
-static struct { unsigned flag:8; char opt_char; } opt_array[] = {
+static struct { unsigned flag:11; char opt_char; } opt_array[] = {
 	{ _DPRINTK_FLAGS_PRINT, 'p' },
 	{ _DPRINTK_FLAGS_INCL_MODNAME, 'm' },
 	{ _DPRINTK_FLAGS_INCL_FUNCNAME, 'f' },
 	{ _DPRINTK_FLAGS_INCL_LINENO, 'l' },
 	{ _DPRINTK_FLAGS_INCL_TID, 't' },
 	{ _DPRINTK_FLAGS_NONE, '_' },
+	{ _DPRINTK_FLAGS_ONCE, 'o' },
+	{ _DPRINTK_FLAGS_PRINTED, 'P' },
+	{ _DPRINTK_FLAGS_RATELIMITED, 'r' },
+	{ _DPRINTK_FLAGS_GROUPED, 'g' },
 	{ _DPRINTK_FLAGS_DELETE_SITE, 'D' },
 };
 
@@ -728,6 +732,30 @@ static inline char *dynamic_emit_prefix(struct _ddebug *desc, char *buf)
 	return buf;
 }
 
+/* test print-once or ratelimited conditions */
+static bool is_onced_or_limited(struct _ddebug *descriptor)
+{
+	if (descriptor->flags & _DPRINTK_FLAGS_ONCE &&
+	    descriptor->flags & _DPRINTK_FLAGS_RATELIMITED)
+		pr_info(" ONCE & RATELIMITED together is nonsense\n");
+
+	if (descriptor->flags & _DPRINTK_FLAGS_ONCE) {
+		if (descriptor->flags & _DPRINTK_FLAGS_PRINTED) {
+			v3pr_info(" would suppress print once\n");
+			// return true;
+		}
+		descriptor->flags |= _DPRINTK_FLAGS_PRINTED;
+		// return false; // wanna see rate stuff
+	}
+	/* test rate-limits */
+	if (descriptor->flags & _DPRINTK_FLAGS_RATELIMITED) {
+		v3pr_info("todo: fetch RLstate{%s}\n",
+			  descriptor->flags & _DPRINTK_FLAGS_GROUPED
+			  ? "grouped" : "solo");
+	}
+	return false;
+}
+
 void __dynamic_pr_debug(struct _ddebug *descriptor, const char *fmt, ...)
 {
 	va_list args;
@@ -737,6 +765,9 @@ void __dynamic_pr_debug(struct _ddebug *descriptor, const char *fmt, ...)
 	BUG_ON(!descriptor);
 	BUG_ON(!fmt);
 
+	if (is_onced_or_limited(descriptor))
+		return;
+
 	va_start(args, fmt);
 
 	vaf.fmt = fmt;
@@ -757,6 +788,9 @@ void __dynamic_dev_dbg(struct _ddebug *descriptor,
 	BUG_ON(!descriptor);
 	BUG_ON(!fmt);
 
+	if (is_onced_or_limited(descriptor))
+		return;
+
 	va_start(args, fmt);
 
 	vaf.fmt = fmt;
@@ -788,6 +822,9 @@ void __dynamic_netdev_dbg(struct _ddebug *descriptor,
 	BUG_ON(!descriptor);
 	BUG_ON(!fmt);
 
+	if (is_onced_or_limited(descriptor))
+		return;
+
 	va_start(args, fmt);
 
 	vaf.fmt = fmt;
@@ -824,6 +861,9 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor,
 	struct va_format vaf;
 	va_list args;
 
+	if (is_onced_or_limited(descriptor))
+		return;
+
 	va_start(args, fmt);
 
 	vaf.fmt = fmt;
-- 
2.31.1