Re: [stable-6.6.y] mm: khugepaged refuses to freeze

[Sergey Senozhatsky <senozhatsky@chromium.org>]

On (26/02/06 10:00), David Hildenbrand (Arm) wrote:
> > > I recall that there is a notifier when the system is preparing to
> > > sleep (pm notifier or something). Could we simply hook into that to
> > > tell khugepaged to suspend+resume?
> > 
> > Do you mean “struct dev_pm_ops”, which is used to register PM callbacks
> > for devices? However, I don’t know how to use it with a kernel thread.
> > 
> > Also look at how kswapd does it, kswapd also uses
> > kthread_freezable_should_stop() to check the freeze state.
> 
> Right, mimicking what kswapd does sound reasonable!

I may be missing something, as I'm not seeing dev_pm_ops in vmscan code.
Would something like this work?

---

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index fa6a018b20a8..c5d89ec223d3 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -394,8 +394,12 @@ static inline int hpage_collapse_test_exit(struct mm_struct *mm)
 
 static inline int hpage_collapse_test_exit_or_disable(struct mm_struct *mm)
 {
+	bool was_frozen;
+	int ret = kthread_freezable_should_stop(&was_frozen);
+
 	return hpage_collapse_test_exit(mm) ||
-		mm_flags_test(MMF_DISABLE_THP_COMPLETELY, mm);
+		mm_flags_test(MMF_DISABLE_THP_COMPLETELY, mm) ||
+		was_frozen || ret;
 }
 
 static bool hugepage_pmd_enabled(void)