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Howlett" , "# 6 . 0 . x" , Andrew Morton , David Hildenbrand , Jonathan Corbet , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , damon@lists.linux.dev, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [RFC PATCH 2/2] Docs/admin-guide/mm/damon/lru_sort: warn commit_inputs vs param updates race Date: Sat, 28 Mar 2026 10:24:13 -0700 Message-ID: <20260328172415.49940-3-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260328172415.49940-1-sj@kernel.org> References: <20260328172415.49940-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: isfnyreyp8imz5tqwwshgr3k3e7rf7gt X-Rspamd-Queue-Id: 2D6DD40007 X-Rspamd-Server: rspam09 X-HE-Tag: 1774718659-665782 X-HE-Meta: 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 tkVZwFlM 6lwvk2tKNclo9MH0lpq4gBrRs1nSbUV82xjUjWA6R2+93zfFx1xb1ymLVFD+hR1R6aV0tKmFOO9E3m7K9ZHIScRrpFXuP3ptFvVUS47O5iQnFRFXvtgSBKDguwzLiEnO8KNsDT/0N67oWK0Ou/nBS9Uxp/QXMAhu48cbxQylXAUAxIGnn4wdEa2G1hAy/iqo8I1WyffVer4bLK0cv/20T+gQtW67MWBI3NBFt8sHzBN74hy0Rox0JjiUpNSAjETsKp0gS4YrAtlAYxa4BIUWC2dnco4yspRMG//O5tPUZ9tPThITP/Q1MGFqYbjoCHi3UPnMWLPQpdJ6a5lFBJCi2b3gsbA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: DAMON_LRU_SORT handles commit_inputs request inside kdamond thread, reading the module parameters. If the user updates the module parameters while the kdamond thread is reading those, races can happen. To avoid this, the commit_inputs parameter shows whether it is still in the progress, assuming users wouldn't update parameters in the middle of the work. Some users might ignore that. Add a warning about the behavior. The issue was discovered [1] by sashiko. [1] https://lore.kernel.org/20260319161620.189392-2-objecting@objecting.org Fixes: 6acfcd0d7524 ("Docs/admin-guide/damon: add a document for DAMON_LRU_SORT") Cc: # 6.0.x Signed-off-by: SeongJae Park --- Documentation/admin-guide/mm/damon/lru_sort.rst | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/Documentation/admin-guide/mm/damon/lru_sort.rst b/Documentation/admin-guide/mm/damon/lru_sort.rst index 797962a459e6..5b8e16394228 100644 --- a/Documentation/admin-guide/mm/damon/lru_sort.rst +++ b/Documentation/admin-guide/mm/damon/lru_sort.rst @@ -79,6 +79,10 @@ of parameters except ``enabled`` again. Once the re-reading is done, this parameter is set as ``N``. If invalid parameters are found while the re-reading, DAMON_LRU_SORT will be disabled. +Once ``Y`` is written to this parametr, the user must not write to any +parameters until reading ``commit_inputs`` again returns ``N``. If users +violate this rule, the kernel can do undefined behaviors. + active_mem_bp ------------- -- 2.47.3