linux-kernel - [RFC PATCH 09/10] dyndbg: add dd_clear

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Message-ID: <20231012194711.3288031-10-jim.cromie@gmail.com>
Date:   Thu, 12 Oct 2023 13:47:10 -0600
From:   Jim Cromie <jim.cromie@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     david@...hat.com, Liam.Howlett@...cle.com, linux-mm@...ck.org,
        Jim Cromie <jim.cromie@...il.com>
Subject: [RFC PATCH 09/10] dyndbg: add dd_clear_range to prune mtrees

Call new dd_clear_range() from ddebug_remove_module().  It calls
mtree_erase() on the trees storing the function, filename, modname
intervals, and passing the 1st descriptor of the interval (ie the
index used on the insert).

dd_clear_range() should properly undo the 3 mtree_insert_ranges done
by dd_store_range.

RFC: it doesnt work as I expected. What am I missing ?

The following log shows that 'rmmod amdgpu' only removes 1 entry from
each maple-tree, not the whole interval.  My index is the 1st
descriptor in each interval.

ISTM (naive reader) this contradicts the documented behavior.

  void *mtree_erase(struct maple_tree *mt, unsigned long index)
  Find an index and erase the entire range.

what is my "entire range" ?

bash-5.2# modprobe amdgpu
....
[   74.256006] dyndbg: attach-client-module:  module:amdgpu nd:4652 nc:0 nu:1
[   74.256968] dyndbg: 4652 debug prints in module amdgpu

bash-5.2# echo 2 > /sys/module/dynamic_debug/parameters/do_scan
[   81.370509] dyndbg: cache: funcs has 3741 entries
[   81.371233] dyndbg: cache: files has 911 entries
[   81.371819] dyndbg: cache: mods has 323 entries

bash-5.2# rmmod amdgpu
[  102.325851] dyndbg: removed module "amdgpu"

bash-5.2# echo 2 > /sys/module/dynamic_debug/parameters/do_scan
[  105.277439] dyndbg: cache: funcs has 3740 entries
[  105.278163] dyndbg: cache: files has 910 entries
[  105.278756] dyndbg: cache: mods has 322 entries

cc: Liam R. Howlett <Liam.Howlett@...cle.com>
cc: linux-mm@...ck.org
Signed-off-by: Jim Cromie <jim.cromie@...il.com>
---
 lib/dynamic_debug.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index fb72a7b05b01..92ffd70a07de 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -1426,6 +1426,14 @@ static void dd_store_range(struct maple_tree *mt, const struct _ddebug *start,
 		v4pr_info("  ok %s at %lx\n", val, first);
 }
 
+static void dd_clear_range(const struct _ddebug *start)
+{
+	v3pr_info("clearing %px\n", start);
+	mtree_erase(&mt_funcs, (unsigned long)start);
+	mtree_erase(&mt_files, (unsigned long)start);
+	mtree_erase(&mt_mods, (unsigned long)start);
+}
+
 #define site_function(s)	(s)->_function
 #define site_filename(s)	(s)->_filename
 #define site_modname(s)		(s)->_modname
@@ -1578,6 +1586,8 @@ static int ddebug_remove_module(const char *mod_name)
 	mutex_lock(&ddebug_lock);
 	list_for_each_entry_safe(dt, nextdt, &ddebug_tables, link) {
 		if (dt->mod_name == mod_name) {
+			/* free mtree entries on descs */
+			dd_clear_range(dt->ddebugs);
 			ddebug_table_free(dt);
 			ret = 0;
 			break;
-- 
2.41.0