linux-kernel - [PATCH] debugobjects: avoid recursive calls with kmemleak

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Message-Id: <20181126165343.2339-1-cai@gmx.us>
Date:   Mon, 26 Nov 2018 11:53:43 -0500
From:   Qian Cai <cai@....us>
To:     akpm@...ux-foundation.org
Cc:     tglx@...utronix.de, longman@...hat.com, yang.shi@...ux.alibaba.com,
        arnd@...db.de, catalin.marinas@....com,
        linux-kernel@...r.kernel.org, Qian Cai <cai@....us>
Subject: [PATCH] debugobjects: avoid recursive calls with kmemleak

CONFIG_DEBUG_OBJECTS_RCU_HEAD does not play well with kmemleak due to
recursive calls.

fill_pool
  kmemleak_ignore
    make_black_object
      put_object
        __call_rcu (kernel/rcu/tree.c)
          debug_rcu_head_queue
            debug_object_activate
              debug_object_init
                fill_pool
                  kmemleak_ignore
                    make_black_object
                      ...

Hence, adding SLAB_NOLEAKTRACE to kmem_cache_create() to not register a
newly allocated debug objects at all.

Suggested-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Qian Cai <cai@....us>
---
 lib/debugobjects.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index eab7727b46ed..55437fd5128b 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -135,7 +135,6 @@ static void fill_pool(void)
 		if (!new)
 			return;
 
-		kmemleak_ignore(new);
 		raw_spin_lock_irqsave(&pool_lock, flags);
 		hlist_add_head(&new->node, &obj_pool);
 		debug_objects_allocated++;
@@ -1128,7 +1127,6 @@ static int __init debug_objects_replace_static_objects(void)
 		obj = kmem_cache_zalloc(obj_cache, GFP_KERNEL);
 		if (!obj)
 			goto free;
-		kmemleak_ignore(obj);
 		hlist_add_head(&obj->node, &objects);
 	}
 
@@ -1182,7 +1180,8 @@ void __init debug_objects_mem_init(void)
 
 	obj_cache = kmem_cache_create("debug_objects_cache",
 				      sizeof (struct debug_obj), 0,
-				      SLAB_DEBUG_OBJECTS, NULL);
+				      SLAB_DEBUG_OBJECTS | SLAB_NOLEAKTRACE,
+				      NULL);
 
 	if (!obj_cache || debug_objects_replace_static_objects()) {
 		debug_objects_enabled = 0;
-- 
2.17.2 (Apple Git-113)