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Howlett" , "# 6 . 0 . x" , 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: [PATCH 2/2] Docs/admin-guide/mm/damon/lru_sort: warn commit_inputs vs param updates race Date: Sun, 29 Mar 2026 08:30:50 -0700 Message-ID: <20260329153052.46657-3-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260329153052.46657-1-sj@kernel.org> References: <20260329153052.46657-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: BFF7C100019 X-Stat-Signature: 6ks8esxszwrmtqtbup51e7x79nejrfib X-Rspamd-Server: rspam06 X-HE-Tag: 1774798257-998395 X-HE-Meta: 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 pgme8jZg A5Uaa1a4ogmB3a6Ez6QTZpiR+QioZhV8Pvfm56TfI0KKwlQ/H1V3xNg7gm1moaD7Rs4jPBtW+9kjvj2vGsYf9mLVF5X6zBtripvaeuVCdCJo2PQdyuGWP7xrHSZCeLmr4H3RgJmio3Jo5FviRkBluoqRa92FPmo0y67/jPLcWjiL7c5SONGSVwk2FY25RUapWPjssPWvsic/OzXDtTh24n2V8PgdAUt+3+UPMjw+f9SA3b/O4YcaBOOnf2zEusvUXdWmAoqBeCadgPXQJbNyGdIenBS0HLpat4yIJ5JeWmKqm2jHtUAWxIRzSyDXgKBUiOfQjNSRoTtXKegfL/9PbBk7gXA== 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..25e2f042a383 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 parameter, the user must not write to any +parameters until reading ``commit_inputs`` again returns ``N``. If users +violate this rule, the kernel may exhibit undefined behavior. + active_mem_bp ------------- -- 2.47.3