Re: [PATCH v2 3/3] drivers/base/memory: fix locking for poison accounting lookup

[Muchun Song]

> On Apr 28, 2026, at 19:37, Miaohe Lin <linmiaohe@xxxxxxxxxx> wrote:
> 
> On 2026/4/28 16:52, Muchun Song wrote:
>> memblk_nr_poison_inc() and memblk_nr_poison_sub() call
>> find_memory_block_by_id(), which requires device_hotplug_lock to
>> serialize the xarray lookup against memory block removal.
>> 
>> Take device_hotplug_lock around the lookup and nr_hwpoison update so
>> the memory block cannot disappear between xa_load() and get_device().
>> 
>> Fixes: 5033091de814 ("mm/hwpoison: introduce per-memory_block hwpoison counter")
>> Cc: stable@xxxxxxxxxxxxxxx
>> Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> 
> Thanks for update.
> 
>> ---
>> drivers/base/memory.c | 10 ++++++++--
>> 1 file changed, 8 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
>> index 6981b55d582a..f76aee29e9a5 100644
>> --- a/drivers/base/memory.c
>> +++ b/drivers/base/memory.c
>> @@ -1228,23 +1228,29 @@ int walk_dynamic_memory_groups(int nid, walk_memory_groups_func_t func,
>> void memblk_nr_poison_inc(unsigned long pfn)
>> {
>> 	const unsigned long block_id = pfn_to_block_id(pfn);
>> - 	struct memory_block *mem = find_memory_block_by_id(block_id);
>> + 	struct memory_block *mem;
>> 
>> + 	lock_device_hotplug();
> 
> memblk_nr_poison_inc() and memblk_nr_poison_sub() are both called from memory_failure() context.
> I'm afraid if memory_failure() is triggered while lock_device_hotplug is held, it will lead to
> deadlock. Or am I miss something?

I am curious is there any place where memory_failure() is called with holding lock_device_hotplug?

Thanks.

> 
> Thanks.
> .