Thread (8 messages) 8 messages, 1 author, 2026-03-28
STALE122d
Revisions (2)
  1. rfc current
  2. v1 [diff vs current]

[RFC PATCH 2/2] Docs/admin-guide/mm/damon/lru_sort: warn commit_inputs vs param updates race

From: SeongJae Park <sj@kernel.org>
Date: 2026-03-28 17:24:18
Also in: damon, linux-mm, lkml, stable
Subsystem: damon, documentation, memory management - misc, the rest · Maintainers: SJ Park, Jonathan Corbet, Andrew Morton, David Hildenbrand, Linus Torvalds

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 (local)

Fixes: 6acfcd0d7524 ("Docs/admin-guide/damon: add a document for DAMON_LRU_SORT")
Cc: <redacted> # 6.0.x
Signed-off-by: SeongJae Park <sj@kernel.org>
---
 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
Keyboard shortcuts
hback out one level
jnext message in thread
kprevious message in thread
ldrill in
Escclose help / fold thread tree
?toggle this help