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

Liu Shixin
2023-09-28T01:22:35Z

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.
>