On 11/08/2011 08:59 PM, Andrea Arcangeli wrote:
> Lack of set_freezable_with_signal() prevented khugepaged to be waken
> up (and prevented to sleep again) across the
> schedule_timeout_interruptible() calls after freezing() becomes
> true. The tight loop in khugepaged_alloc_hugepage() also missed one
> try_to_freeze() call in case alloc_hugepage() would repeatedly fail in
> turn preventing the loop to break and to reach the try_to_freeze() in
> the khugepaged main loop.
>
> khugepaged would still freeze just fine by trying again the next
> minute but it's better if it freezes immediately.
>
> Reported-by: Jiri Slaby <jslaby@xxxxxxx>
> Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> ---
> mm/huge_memory.c | 3 ++-
> 1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 4298aba..67311d1 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2277,6 +2277,7 @@ static struct page *khugepaged_alloc_hugepage(void)
> if (!hpage) {
> count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
> khugepaged_alloc_sleep();
> + try_to_freeze();
> } else
> count_vm_event(THP_COLLAPSE_ALLOC);
> } while (unlikely(!hpage) &&
> @@ -2331,7 +2332,7 @@ static int khugepaged(void *none)
> {
> struct mm_slot *mm_slot;
>
> - set_freezable();
> + set_freezable_with_signal();
> set_user_nice(current, 19);
>
> /* serialize with start_khugepaged() */
>
Why do we need to use both set_freezable_with_signal() and an additional
try_to_freeze()? Won't just using either one of them be good enough?
Or am I missing something here?
Thanks,
Srivatsa S. Bhat
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