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b=CMjCj8vmTGMiEd6DlOjN+Y2aaH5NimELhZqNChgYdwJgOvY4OgK/i2XMjYRetaipF KmaJxhyyoZkkwBFBkYY0ymUjP6vUhPz5qEswXUI60vZzOMWPrzejeHotR5Sdi2NSm/ d7rmm5r8VhuBAjnXlfani90BT28mhqSDRRV6r7Y2puL53IYxDLo0fJ8iRzErtg4NCq XyT+0pONtW8Iww5Gph6rKCE/+/QFk8xb12BhA9ITQcy55IUxTUlNkoMYYn0AYeclgb 27T2nK7TDHwrVjC1ORiWKmOWGESYOyKeHiM3nE3Yc/6pRMIJand7SRPhG5nFcuCYw/ xxFQ2FJ8uBIxg== From: SJ Park To: IgorpetinDev Cc: SJ Park , akpm@linux-foundation.org, damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/damon/vaddr: remove redundant RCU lock Date: Mon, 29 Jun 2026 18:00:32 -0700 Message-ID: <20260630010032.141941-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260629165349.4260-1-igorpetindev@gmail.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 17ABCA000D X-Rspam-User: X-Stat-Signature: gjsxkk7wjdxrmfx3wsf8xr4yijatbcbw X-HE-Tag: 1782781242-915301 X-HE-Meta: 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 k2R+YndM 7LffejNNZq2Q5p69WRX+dNApD1muVny2gqpEoHiqjGCRrCNldbEoauNuovb18fn+5uWatgloLFNAcBl7UGte89I1ZgeCK5zdMsRHhwrLKMQgXQPOuz/3F4IW9M8pZfTF1zJRqfG6C8sFcZyHFYebO9doo/fGP7ePFudW424rF2uk069PcA973IWoWXjjm5i+fbI17VNz0W2hCnO5lezTnDyG0/6Yvvj4TAqY+TBf+Sy2fJc52dtqN56U7X5z3Jh3KkrlN Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 29 Jun 2026 19:53:49 +0300 IgorpetinDev wrote: > __damon_va_three_regions() is called only by damon_va_three_regions(), > which already holds mmap_read_lock(). Since mmap_read_lock() is held, > the maple tree and VMA list are protected from concurrent changes. > Remove the unnecessary rcu_read_lock() and rcu_read_unlock() calls. > > Signed-off-by: IgorpetinDev We prefer using a real name. I show you used 'Igor Putko' as your name before. Any reason to change the name? > --- > mm/damon/vaddr.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c > index d27147603..345b89b5d 100644 > --- a/mm/damon/vaddr.c > +++ b/mm/damon/vaddr.c > @@ -84,7 +84,6 @@ static int __damon_va_three_regions(struct mm_struct *mm, > * If this is too slow, it can be optimised to examine the maple > * tree gaps. > */ > - rcu_read_lock(); > for_each_vma(vmi, vma) { > unsigned long gap; > > @@ -105,7 +104,6 @@ static int __damon_va_three_regions(struct mm_struct *mm, > next: > prev = vma; > } > - rcu_read_unlock(); As Sashiko also commented, this may cause lockdep warning. Actually this was added to fix it. Refer to the previous discussions [1] for more details. How about moving rcu_read_[un]lock() to the caller test code? [1] https://lore.kernel.org/20240904004534.1189-1-sj@kernel.org Thanks, SJ [...]