Re: [PATCH] mm/madvise: add cond_resched() in THP branch of madvise_cold_or_pageout_pte_range()

[Gregory Price <gourry@gourry.net>]

On Sat, Oct 10, 2026 at 10:40:42AM +0800, albin_yang@163.com wrote:
> From: Wei Yang <albinwyang@tencent.com>
> 
> Crash log:
>   watchdog: BUG: soft lockup - CPU#63 stuck for 23s! [stress-ng-vm:1665914]
>   ...
>   Call trace:
>   pmdp_invalidate+0x48/0x68
>   madvise_cold_or_pageout_pte_range+0x84c/0xb00
>   walk_pmd_range.isra.0+0x1ac/0x3b0
>   walk_pud_range+0x120/0x190
>   walk_pgd_range+0x170/0x1b8
>   __walk_page_range+0x184/0x198
>   walk_page_range_vma+0x94/0x128
>   madvise_cold+0xd8/0x198
>   madvise_vma_behavior+0x234/0x638
>   madvise_walk_vmas.constprop.0+0xdc/0x210
>   madvise_do_behavior+0xa8/0x328
>   do_madvise+0xd8/0x140
>   __arm64_sys_madvise+0x2c/0xe0
> 
> Signed-off-by: Wei Yang <albinwyang@tencent.com>
> ---
>  mm/madvise.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/madvise.c b/mm/madvise.c
> index eeee82cf2b3f..0755e6d99757 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -450,6 +450,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
>  		spin_unlock(ptl);
>  		if (pageout)
>  			reclaim_pages(&folio_list);
> +		cond_resched();
>  		return 0;
>  	}
> 

This same improvement came naturally from refactoring the entire
function into a proper pagewalk structure:

https://lore.kernel.org/linux-mm/20260922235830.2350770-10-gourry@gourry.net/

this function is really nasty.

~Gregory