[PATCH 09/11] dynamic_debug: add_to_pending() saves non-matching queries for later.

[Jim Cromie]

When a query/rule doesnt match, call add_to_pending(new function)
to copy the query off the stack, into a (new) struct pending_query,
and add to pending_queries (new) list.

Patch adds: /sys/module/dynamic_debug/parameters/
  verbose - rw, added previously, here for completeness
  pending_ct - ro, shows current count of pending queries
  pending_max - rw, set max pending, further pending queries are rejected

With this and previous patches, queries added on the boot-line which
do not match (because module is not built-in, and thus not present yet)
are added to pending_queries.

IE, with these boot-line additions:
 dynamic_debug.verbose=1 ddebug_query="module scx200_hrt +p"

Kernel will log the following:

ddebug_exec_queries: query 0: "module scx200_hrt +p"
ddebug_tokenize: split into words: "module" "scx200_hrt" "+p"
ddebug_parse_query: parsed q->function="(null)" q->filename="(null)" q->module="scx200_hrt" q->format="(null)" q->lineno=0-0
ddebug_parse_flags: op='+'
ddebug_parse_flags: flags=0x1
ddebug_parse_flags: *flagsp=0x1 *maskp=0xffffffff
ddebug_exec_query: nfound 0 on q->function="(null)" q->filename="(null)" q->module="scx200_hrt" q->format="(null)" q->lineno=0-0
ddebug_add_to_pending: add to pending: q->function="(null)" q->filename="(null)" q->module="scx200_hrt" q->format="(null)" q->lineno=0-0
ddebug_add_to_pending: ddebug: query saved as pending 1

Signed-off-by: Jim Cromie <jim.cromie@xxxxxxxxx>
---
 lib/dynamic_debug.c |   78 +++++++++++++++++++++++++++++++++++++++++++++++----
 1 files changed, 72 insertions(+), 6 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 9b8b1e8..37d0275 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -53,6 +53,16 @@ struct ddebug_query {
 	unsigned int first_lineno, last_lineno;
 };
 
+struct pending_query {
+	struct list_head link;
+	struct ddebug_query query;
+	char filename[100];
+	char module[30];
+	char function[50];
+	char format[200];
+	unsigned int flags, mask;
+};
+
 struct ddebug_iter {
 	struct ddebug_table *table;
 	unsigned int idx;
@@ -61,7 +71,13 @@ struct ddebug_iter {
 static DEFINE_MUTEX(ddebug_lock);
 static LIST_HEAD(ddebug_tables);
 static int verbose = 0;
-module_param(verbose, int, 0744);
+module_param(verbose, int, 0644);
+
+/* legal but inapplicable queries, save and test against new modules */
+static LIST_HEAD(pending_queries);
+static int pending_ct, pending_max = 100;
+module_param(pending_ct, int, 0444);
+module_param(pending_max, int, 0644);
 
 /* Return the last part of a pathname */
 static inline const char *basename(const char *path)
@@ -96,6 +112,56 @@ static char *ddebug_describe_flags(struct _ddebug *dp, char *buf,
 	return buf;
 }
 
+static char prbuf_query[300];
+
+static char *show_ddebug_query(const struct ddebug_query *q)
+{
+        sprintf(prbuf_query,
+		"q->function=\"%s\" q->filename=\"%s\" "
+		"q->module=\"%s\" q->format=\"%s\" q->lineno=%u-%u",
+		q->function, q->filename, q->module, q->format,
+		q->first_lineno, q->last_lineno);
+
+	return prbuf_query;
+}
+
+/* copy query off stack, save flags & mask, and store in pending-list */
+static void add_to_pending(const struct ddebug_query *query,
+			   unsigned int flags, unsigned int mask)
+{
+	struct pending_query *pq;
+
+	if (pending_ct >= pending_max) {
+		pr_warn("ddebug: no matches for query, pending is full\n");
+		return;
+	}
+	if (verbose)
+		pr_info("add to pending: %s\n", show_ddebug_query(query));
+
+	pending_ct++;
+	pq = kzalloc(sizeof(struct pending_query), GFP_KERNEL);
+
+	/* copy non-null match-specs into allocd mem, update pointers */
+	if (query->module)
+		pq->query.module = strcpy(pq->module, query->module);
+	if (query->function)
+		pq->query.function = strcpy(pq->function, query->function);
+	if (query->filename)
+		pq->query.filename = strcpy(pq->filename, query->filename);
+	if (query->format)
+		pq->query.format = strcpy(pq->format, query->format);
+
+	pq->flags = flags;
+	pq->mask = mask;
+
+	mutex_lock(&ddebug_lock);
+	list_add(&pq->link, &pending_queries);
+	mutex_unlock(&ddebug_lock);
+
+	if (verbose)
+		pr_info("ddebug: query saved as pending %d\n", pending_ct);
+}
+
 /*
  * Search the tables for _ddebug's which match the given
  * `query' and apply the `flags' and `mask' to them.  Tells
@@ -348,11 +414,7 @@ static int ddebug_parse_query(char *words[], int nwords,
 	}
 
 	if (verbose)
-		pr_info("q->function=\"%s\" q->filename=\"%s\" "
-		       "q->module=\"%s\" q->format=\"%s\" q->lineno=%u-%u\n",
-			query->function, query->filename,
-			query->module, query->format, query->first_lineno,
-			query->last_lineno);
+		pr_info("parsed %s\n", show_ddebug_query(query));
 
 	return 0;
 }
@@ -437,6 +499,10 @@ static int ddebug_exec_query(char *query_string)
 	/* actually go and implement the change */
 	nfound = ddebug_change(&query, flags, mask);
 
+	pr_info("nfound %d on %s\n", nfound, show_ddebug_query(&query));
+	if (!nfound)
+		ddebug_add_to_pending(&query, flags, mask);
+
 	return 0;
 }
 
-- 
1.7.4.1

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