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From: "Brendan Jackman" To: "Harry Yoo" , "Brendan Jackman" , "Andrew Morton" , "Vlastimil Babka" , "Suren Baghdasaryan" , "Michal Hocko" , "Johannes Weiner" , "Zi Yan" Cc: "Alexei Starovoitov" , , Subject: Re: [PATCH] mm/page_alloc: document that alloc_pages_nolock() uses RCU References: <20260519-nolock-rcu-comment-v1-1-4a630c8794e5@google.com> <6c089de3-34d9-4dd9-9646-f51328c77497@kernel.org> In-Reply-To: <6c089de3-34d9-4dd9-9646-f51328c77497@kernel.org> X-Migadu-Flow: FLOW_OUT X-Stat-Signature: ixkgi4frhbj5xkw48sjonm88pipchsur X-Rspamd-Queue-Id: C507B40017 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1779790459-584983 X-HE-Meta: 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 N730ZXKK WfMN1w0n6v6wwLG3z2DaTP+EGn4eLXRigcC6+Ahxqo4hl8dJambWGSGoohHsic65pr9KUDE6MmFR5LxWFJq2vzKHBMNq1HyHL5dwos5lVqzJ8bGKCcQPzjc/gIqeC/uQAFsQg9qF6mrHAZiVIhg+a5+5DXMuJJvq8tKwKUJQaskaAJUMR2Kq7wmvzbH/Y8+qMsCJTOxCXIsXJN4b8BwNNSGuZEnLN9pi5jxlwO2OOD63DXZw9ieO2mtKnZNjwdQQs1MAyaBEm1VKJCbIsWlh8yBbqN8SNsB4lROOkLEvkJ80RqT2nk7pD0uQ7/w== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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= =20 > 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. >>=20 >> Suggested-by: Junaid Shahid > > The email should be junaids@google.com, not jackmanb@google.com? ;) Damn. It looks like this already went into mm-unstable but I guess it's not a huge deal.