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

[Miaohe Lin]

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?

Thanks.
.