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Howlett" , "# 5 . 19 . 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 1/2] Docs/admin-guide/mm/damon/reclaim: warn commit_inputs vs param updates race Date: Sun, 29 Mar 2026 08:30:49 -0700 Message-ID: <20260329153052.46657-2-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-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 32D68A0005 X-Stat-Signature: bzgbag87cyzjm9fkw8jah9ipyayyd8ji X-Rspam-User: X-HE-Tag: 1774798257-348076 X-HE-Meta: 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 s9lXdjA4 lfy7MsCgyjWL/I2kWncxIenDtexyD9LM4juhF4h5kP2ZAp9w6xdQdqzFCVJU7RM+4GPfAouq0APftawKZ17Uq0w41UbdEACSznKsapEM2eC3n6wtiu6a2tqoI4hdPaUG0UbGZ8mDNUeT0ktSz4thq7rU3x5xyUwVyxyRn/yQOI7hStZdrUfabPRPt1Ae6Y2YAuQXTNIPM79PqSBSaMG5PIZlfh+ay0+WgxvZl4XXb297RuG04NBpoLjczZMDNVD0rdWPjvW2vox7FmYl+0gBouG74lPcXXk73So2yGKrjYiJuvBFikZjhlFn9XRsg3+j1DXYqzT3NFO9hrc2I8zTRRFACsw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: DAMON_RECLAIM 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/20260319161620.189392-3-objecting@objecting.org Fixes: 81a84182c343 ("Docs/admin-guide/mm/damon/reclaim: document 'commit_inputs' parameter") Cc: # 5.19.x Signed-off-by: SeongJae Park --- Documentation/admin-guide/mm/damon/reclaim.rst | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/Documentation/admin-guide/mm/damon/reclaim.rst b/Documentation/admin-guide/mm/damon/reclaim.rst index a100216f3a72..17e938c319e3 100644 --- a/Documentation/admin-guide/mm/damon/reclaim.rst +++ b/Documentation/admin-guide/mm/damon/reclaim.rst @@ -71,6 +71,10 @@ 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_RECLAIM 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. + min_age ------- -- 2.47.3