Re: [PATCH] mm/khugepaged: Allow to interrupt allocation sleep again

[Vlastimil Babka <vbabka@suse.cz>]

On 08/24/2015 05:13 PM, Petr Mladek wrote:
> The commit 1dfb059b9438633b0546 ("thp: reduce khugepaged freezing
> latency") fixed khugepaged to do not block a system suspend. But
> the result is that it could not get interrupted before the given
> timeout because the condition for the wait event is "false".
>
> This patch puts back the original approach but it uses
> freezable_schedule_timeout_interruptible() instead of
> schedule_timeout_interruptible(). It does the right thing.
> I am pretty sure that the freezable variant was not used in
> the original fix only because it was not available at that time.
>
> The regression has been there for ages. It was not critical. It just
> did the allocation throttling a little bit more aggressively.
>
> I found this problem when converting the kthread to kthread worker API
> and trying to understand the code.
>
> Signed-off-by: Petr Mladek <pmladek@suse.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
>   mm/huge_memory.c | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 7109330c5911..eb115aaa429c 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2368,8 +2368,12 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
>
>   static void khugepaged_alloc_sleep(void)
>   {
> -	wait_event_freezable_timeout(khugepaged_wait, false,
> -			msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
> +	DEFINE_WAIT(wait);
> +
> +	add_wait_queue(&khugepaged_wait, &wait);
> +	freezable_schedule_timeout_interruptible(
> +		msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
> +	remove_wait_queue(&khugepaged_wait, &wait);
>   }
>
>   static int khugepaged_node_load[MAX_NUMNODES];
>