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SubjectRe: [PATCH] sched: Avoid that __wait_on_bit_lock() hangs
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On 08/10/2016 03:46 AM, Oleg Nesterov wrote:
> OK. Could you try another debugging patch below?
>
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index e5a3244..9d5f892 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -711,6 +711,15 @@ static inline int page_has_private(struct page *page)
> return !!(page->flags & PAGE_FLAGS_PRIVATE);
> }
>
> +void unlock_page(struct page *page);
> +static inline void __ClearPageLocked_x(struct page *page)
> +{
> + if (PageLocked(compound_head(page)))
> + unlock_page(page);
> +}
> +
> +#define __ClearPageLocked(page) __ClearPageLocked_x(page)
> +
> #undef PF_ANY
> #undef PF_HEAD
> #undef PF_NO_TAIL

Hello Oleg,

That's an excellent catch. With your previous patch and this patch
applied I can't reproduce the hang in truncate_inode_pages_range()
anymore. I still see some other wait_on_page_bit() hangs after an I/O
error has occurred. However, the hangs that I still see are related to
waiting on buffer head state changes and not on the PG_locked page flag.

Thanks,

Bart.

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