The patch titled
Subject: mm/damon/reclaim: schedule 'damon_reclaim_timer' only after 'system_wq' is initialized
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-damon-reclaim-schedule-damon_reclaim_timer-only-after-system_wq-is-initialized.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-reclaim-schedule-damon_reclaim_timer-only-after-system_wq-is-initialized.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: SeongJae Park <sj@xxxxxxxxxx>
Subject: mm/damon/reclaim: schedule 'damon_reclaim_timer' only after 'system_wq' is initialized
Date: Sat, 4 Jun 2022 19:50:51 +0000
Commit 059342d1dd4e ("mm/damon/reclaim: fix the timer always stays
active") made DAMON_RECLAIM's 'enabled' parameter store callback,
'enabled_store()', to schedule 'damon_reclaim_timer'. The scheduling uses
'system_wq', which is initialized in 'workqueue_init_early()'. As kernel
parameters parsing function ('parse_args()') is called before
'workqueue_init_early()', 'enabled_store()' can be executed before
'workqueue_init_early()' and end up accessing the uninitialized
'system_wq'. As a result, the booting hang[1]. This commit fixes the
issue by checking if the initialization is done before scheduling the
timer.
[1] https://lkml.kernel.org/20220604192222.1488-1-sj@xxxxxxxxxx/
Link: https://lkml.kernel.org/r/20220604195051.1589-1-sj@xxxxxxxxxx
Fixes: 059342d1dd4e ("mm/damon/reclaim: fix the timer always stays active")
Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
Reported-by: Greg White <gwhite@xxxxxxxxxxx>
Cc: Hailong Tu <tuhailong@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/damon/reclaim.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/mm/damon/reclaim.c~mm-damon-reclaim-schedule-damon_reclaim_timer-only-after-system_wq-is-initialized
+++ a/mm/damon/reclaim.c
@@ -374,6 +374,8 @@ static void damon_reclaim_timer_fn(struc
}
static DECLARE_DELAYED_WORK(damon_reclaim_timer, damon_reclaim_timer_fn);
+static bool damon_reclaim_initialized;
+
static int enabled_store(const char *val,
const struct kernel_param *kp)
{
@@ -382,6 +384,10 @@ static int enabled_store(const char *val
if (rc < 0)
return rc;
+ /* system_wq might not initialized yet */
+ if (!damon_reclaim_initialized)
+ return rc;
+
if (enabled)
schedule_delayed_work(&damon_reclaim_timer, 0);
@@ -449,6 +455,8 @@ static int __init damon_reclaim_init(voi
damon_add_target(ctx, target);
schedule_delayed_work(&damon_reclaim_timer, 0);
+
+ damon_reclaim_initialized = true;
return 0;
}
_
Patches currently in -mm which might be from sj@xxxxxxxxxx are
mm-damon-reclaim-schedule-damon_reclaim_timer-only-after-system_wq-is-initialized.patch
docs-admin-guide-damon-reclaim-remove-a-paragraph-that-been-obsolete-due-to-online-tuning-support.patch
mm-damon-dbgfssysfs-move-target_has_pid-from-dbgfs-to-damonh.patch
mm-damon-reclaim-deduplicate-commit_inputs-handling.patch
mm-damon-sysfs-deduplicate-inputs-applying.patch
mm-damon-reclaim-make-enabled-checking-timer-simpler.patch
mm-damon-reclaim-add-damon_reclaim_-prefix-to-enabled_store.patch
