linux-kernel - Re: [PATCH 2/3] mm/kmemleak: fix partially freeing unknown object warning

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Date:   Thu, 28 Sep 2023 09:22:27 +0800
From:   Liu Shixin <liushixin2@...wei.com>
To:     Catalin Marinas <catalin.marinas@....com>
CC:     Patrick Wang <patrick.wang.shcn@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] mm/kmemleak: fix partially freeing unknown object
 warning



On 2023/9/28 1:06, Catalin Marinas wrote:
> On Wed, Sep 27, 2023 at 11:59:22AM +0800, Liu Shixin wrote:
>> diff --git a/mm/kmemleak.c b/mm/kmemleak.c
>> index 54c2c90d3abc..5a2bbd85df57 100644
>> --- a/mm/kmemleak.c
>> +++ b/mm/kmemleak.c
>> @@ -208,6 +208,8 @@ static struct rb_root object_tree_root = RB_ROOT;
>>  static struct rb_root object_phys_tree_root = RB_ROOT;
>>  /* protecting the access to object_list, object_tree_root (or object_phys_tree_root) */
>>  static DEFINE_RAW_SPINLOCK(kmemleak_lock);
>> +/* Serial delete_object_part() to ensure all objects is deleted correctly */
>> +static DEFINE_RAW_SPINLOCK(delete_object_part_mutex);
> Don't call this mutex, it implies sleeping.
Sorry, I used to define it as a mutex lock and forgot to change it.
>
>>  
>>  /* allocation caches for kmemleak internal data */
>>  static struct kmem_cache *object_cache;
>> @@ -784,13 +786,16 @@ static void delete_object_part(unsigned long ptr, size_t size, bool is_phys)
>>  {
>>  	struct kmemleak_object *object;
>>  	unsigned long start, end;
>> +	unsigned long flags;
>>  
>> +	raw_spin_lock_irqsave(&delete_object_part_mutex, flags);
>>  	object = find_and_remove_object(ptr, 1, is_phys);
>>  	if (!object) {
>>  #ifdef DEBUG
>>  		kmemleak_warn("Partially freeing unknown object at 0x%08lx (size %zu)\n",
>>  			      ptr, size);
>>  #endif
>> +		raw_spin_unlock_irqrestore(&delete_object_part_mutex, flags);
> I prefer a goto out and a single place for unlocking.
>
> However, we already take the kmemleak_lock in find_and_remove_object().
> So better to open-code that function here and avoid introducing a new
> lock. __create_object() may need a new bool argument, no_lock or
> something. Or just split it into separate functions for allocating the
> kmemleak structure and adding it to the corresponding trees/lists under
> a lock.
>