[merged mm-stable] mm-damon-core-document-damon_call-damon_start-race-hang-issue.patch removed from -mm tree

[merged mm-stable] mm-damon-core-document-damon_call-damon_start-race-hang-issue.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm/damon/core: document damon_call()/damon_start() race hang issue
has been removed from the -mm tree.  Its filename was
     mm-damon-core-document-damon_call-damon_start-race-hang-issue.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: SJ Park <sj@kernel.org>
Subject: mm/damon/core: document damon_call()/damon_start() race hang issue
Date: Thu, 17 Sep 2026 07:22:03 -0700

Let's suppose damon_start() and damon_call() are executed in parallel
for the same DAMON context.  Then, damon_call() could show
ctx->damon_calls_obsolete set while ctx->kdamond is unset.  If
damon_start() sets ctx->kdamond before damon_call() starts the
cancelling, damon_call() can indefinitely hang.  No DAMON API caller
does such parallel execution of damon_start() and damon_call(), so the
issue doesn't exist.  But who knows what will happen in future.  Add a
clarification comment for caution.

Link: https://lore.kernel.org/20260917142210.90829-6-sj@kernel.org
Signed-off-by: SJ Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Asier Gutierrez <gutierrez.asier@huawei-partners.com>
Cc: Brendan Higgins <brendan.higgins@linux.dev>
Cc: David Gow <davidgow@davidgow.net>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
---

 mm/damon/core.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/mm/damon/core.c~mm-damon-core-document-damon_call-damon_start-race-hang-issue
+++ a/mm/damon/core.c
@@ -2258,6 +2258,9 @@ int damon_kdamond_pid(struct damon_ctx *
  *
  * When this function is failed, the @ctx is guaranteed to be stopped.
  *
+ * This function should not be called in parallel to damon_start() for the
+ * @ctx.  In the case, this function could indefinitely hang.
+ *
  * Return: 0 on success, negative error code otherwise.
  */
 int damon_call(struct damon_ctx *ctx, struct damon_call_control *control)
_

Patches currently in -mm which might be from sj@kernel.org are

mm-damon-core-introduce-damos_quota_goal-complement.patch
mm-damon-core-add-complement-argument-to-damos_new_quota_goal.patch
mm-damon-sysfs-schemes-support-quota-goal-complement-flag.patch
mm-damon-tests-core-kunit-test-quota_goal-complement-commit.patch
selftests-damon-sysfssh-test-quota-goal-complement-flag-file.patch
docs-mm-damon-design-document-damos-quota-goal-complement-flag.patch
docs-admin-guide-mm-damon-usage-update-for-quota-goal-complement-file.patch
docs-abi-damon-update-for-quota-goal-metric-complement-sysfs-file.patch