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mm/damon/reclaim: schedule 'damon_reclaim_timer' only after 'system_wq' is initialized 

Commit 059342d1dd ("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: 059342d1dd ("mm/damon/reclaim: fix the timer always stays active")
Signed-off-by: SeongJae Park <sj@kernel.org>
Reported-by: Greg White <gwhite@kupulau.com>
Cc: Hailong Tu <tuhailong@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
SeongJae Park 2022-06-04 19:50:51 +00:00 committed by akpm
parent d25c83c660
commit 2949282938
1 changed files with 8 additions and 0 deletions
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8
mm/damon/reclaim.c
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@ -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;
}