linux-kernel - Re: [stable-6.6.y] mm: khugepaged refuses to freeze

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Message-ID: <a2985ffb-6f00-4b0b-b29d-22b39ffc9eb0@kernel.org>
Date: Tue, 10 Feb 2026 11:21:12 +0100
From: "David Hildenbrand (Arm)" <david@...nel.org>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>,
 Sergey Senozhatsky <senozhatsky@...omium.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Zi Yan <ziy@...dia.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, Nico Pache <npache@...hat.com>,
 Ryan Roberts <ryan.roberts@....com>, Dev Jain <dev.jain@....com>,
 Barry Song <baohua@...nel.org>, Lance Yang <lance.yang@...ux.dev>,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [stable-6.6.y] mm: khugepaged refuses to freeze

On 2/10/26 11:07, Baolin Wang wrote:
> 
> 
> On 2/10/26 11:21 AM, Sergey Senozhatsky wrote:
>> On (26/02/06 10:00), David Hildenbrand (Arm) wrote:
>>>
>>> Right, mimicking what kswapd does sound reasonable!
>>
>> I may be missing something, as I'm not seeing dev_pm_ops in vmscan code.
>> Would something like this work?
>>
>> ---
>>
>> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
>> index fa6a018b20a8..c5d89ec223d3 100644
>> --- a/mm/khugepaged.c
>> +++ b/mm/khugepaged.c
>> @@ -394,8 +394,12 @@ static inline int hpage_collapse_test_exit(struct 
>> mm_struct *mm)
>>   static inline int hpage_collapse_test_exit_or_disable(struct 
>> mm_struct *mm)
>>   {
>> +    bool was_frozen;
>> +    int ret = kthread_freezable_should_stop(&was_frozen);
>> +
>>       return hpage_collapse_test_exit(mm) ||
>> -        mm_flags_test(MMF_DISABLE_THP_COMPLETELY, mm);
>> +        mm_flags_test(MMF_DISABLE_THP_COMPLETELY, mm) ||
>> +        was_frozen || ret;
>>   }
> 
> Since the hpage_collapse_test_exit_or_disable() can be called by 
> madvise_callapse(), which is not a kernel thread. 

Which raises the question whether we should forward that context 
(khugepaged vs. madvise) to hpage_collapse_test_exit_or_disable().

-- 
Cheers,

David