From 2949282938135ab734c3829495ae393523ceb702 Mon Sep 17 00:00:00 2001 From: SeongJae Park Date: Sat, 4 Jun 2022 19:50:51 +0000 Subject: [PATCH] mm/damon/reclaim: schedule 'damon_reclaim_timer' only after 'system_wq' is initialized 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@kernel.org/ Link: https://lkml.kernel.org/r/20220604195051.1589-1-sj@kernel.org Fixes: 059342d1dd4e ("mm/damon/reclaim: fix the timer always stays active") Signed-off-by: SeongJae Park Reported-by: Greg White Cc: Hailong Tu Signed-off-by: Andrew Morton --- mm/damon/reclaim.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/mm/damon/reclaim.c b/mm/damon/reclaim.c index 8efbfb2..4b07c29 100644 --- a/mm/damon/reclaim.c +++ b/mm/damon/reclaim.c @@ -374,6 +374,8 @@ static void damon_reclaim_timer_fn(struct work_struct *work) } 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(void) damon_add_target(ctx, target); schedule_delayed_work(&damon_reclaim_timer, 0); + + damon_reclaim_initialized = true; return 0; } -- 2.7.4