On 2022/12/6 5:03, Andrew Morton wrote:
On Mon, 5 Dec 2022 22:03:27 +0800 Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote:
When handle MADV_WILLNEED in madvise(), the soflockup may be occurred
in swapin_walk_pmd_entry() if swapin lots of memory on slow device,
add a cond_resched() into it to avoid the possible softlockup.
...
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -226,6 +226,7 @@ static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,
put_page(page);
}
swap_read_unplug(splug);
+ cond_resched();
return 0;
}
I wonder if this would be better in walk_pmd_range(), to address other
very large walk attempts.
mm/madvise.c:287: walk_page_range(vma->vm_mm, start, end,
&swapin_walk_ops, vma);
mm/madvise.c:514: walk_page_range(vma->vm_mm, addr, end,
&cold_walk_ops, &walk_private);
mm/madvise.c:762: walk_page_range(vma->vm_mm, range.start, range.end,
mm/madvise.c-763- &madvise_free_walk_ops, &tlb);
The cold_walk_ops and madvise_free_walk_ops are already with cond_resched()
in theirs pmd_entry walk, maybe there's no need for a precautionary increase
a cond_resched() for now
.
