Re: [PATCH] mm/page_alloc: document that alloc_pages_nolock() uses RCU

[Vlastimil Babka (SUSE)]

On 5/26/26 12:14 PM, Brendan Jackman wrote:
> On Wed May 20, 2026 at 5:16 AM CEST, Harry Yoo wrote:
>>  > (I don't think there is even> any documentation of what noinstr means 
>> at all, let alone the connection
>>> with RCU).
>>
>> *flips through the documentation*
>> Oh, perhaps Documentation/core-api/entry.rst?
> 
> Oh, you're right. The situation is way better than I thought, and now
> I realise I have read this and it's probably where I learned about
> this in the first place (I thought I learned it all from Junaid). I
> apologise to the Documentation/ tree for my slander.
> 
>>> Note this is not claiming that any cgroup code called from the allocator
>>> would actually break if this restriction was violated, it could very
>>> well be that there's no real way for the allocator to act on a cgroup
>>> that can disappear concurrently. But, since it's likely nobody has
>>> verified this one way or another, better to just be safe and declare
>>> that RCU is required. Allocating from an RCU-unsafe context seems a bit
>>> crazy anyway.
>>>
>>> Suggested-by: Junaid Shahid <jackmanb@xxxxxxxxxx>
>>
>> The email should be junaids@xxxxxxxxxx, not jackmanb@xxxxxxxxxx? ;)
> 
> Damn. It looks like this already went into mm-unstable but I guess
> it's not a huge deal.

Things in mm-unstable can be fixed up. That's why "unstable".

Acked-by: Vlastimil Babka (SUSE) <vbabka@xxxxxxxxxx>