Re: [PATCH] mm: ksm: Remove unnecessary try_to_freeze()

[David Hildenbrand <david@redhat.com>]

On 13.12.23 10:09, Kevin Hao wrote:
> A freezable kernel thread can enter frozen state during freezing by
> either calling try_to_freeze() or using wait_event_freezable() and its
> variants. However, there is no need to use both methods simultaneously.
> 
> Signed-off-by: Kevin Hao <haokexin@gmail.com>
> Cc: Andrea Arcangeli <aarcange@redhat.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Cc: Pavel Machek <pavel@ucw.cz>
> ---
>   mm/ksm.c | 4 +---
>   1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/mm/ksm.c b/mm/ksm.c
> index 16532fa85a46..e2ce850c2739 100644
> --- a/mm/ksm.c
> +++ b/mm/ksm.c
> @@ -2604,11 +2604,9 @@ static int ksm_scan_thread(void *nothing)
>   			ksm_do_scan(ksm_thread_pages_to_scan);
>   		mutex_unlock(&ksm_thread_mutex);
>   
> -		try_to_freeze();
> -
>   		if (ksmd_should_run()) {
>   			sleep_ms = READ_ONCE(ksm_thread_sleep_millisecs);
> -			wait_event_interruptible_timeout(ksm_iter_wait,
> +			wait_event_freezable_timeout(ksm_iter_wait,
>   				sleep_ms != READ_ONCE(ksm_thread_sleep_millisecs),
>   				msecs_to_jiffies(sleep_ms));
>   		} else {

I'm not an expert on task freezing, but staring at 
Documentation/power/freezing-of-tasks.txt

"freezable kernel threads need to call it
explicitly in suitable places or use the wait_event_freezable() or
wait_event_freezable_timeout() macros (defined in 
include/linux/freezer.h) that combine interruptible sleep with checking 
if the task is to be frozen and calling try_to_freeze()."

So this cleanup makes sense to me.

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb