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

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Message-ID: <f42cacfd-e97d-7471-f520-619fbbee63ff@redhat.com>
Date:   Mon, 26 Nov 2018 12:10:14 -0500
From:   Waiman Long <longman@...hat.com>
To:     Qian Cai <cai@....us>, akpm@...ux-foundation.org
Cc:     tglx@...utronix.de, yang.shi@...ux.alibaba.com, arnd@...db.de,
        catalin.marinas@....com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] debugobjects: avoid recursive calls with kmemleak

On 11/26/2018 11:53 AM, Qian Cai wrote:
> 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;

Acked-by: Waiman Long <longman@...hat.com>