Hi, Longlong,
Longlong Xia <xialonglong1@xxxxxxxxxx> writes:
> We found that the plist_for_each_entry_safe() loop in get_swap_pages()
> could reach tens of thousands of times to find available space (extreme
> case: cond_resched() is not called in the loop). The test scenario is like
> commit de1ccfb64824 ("swapfile: fix soft lockup in scan_swap_map_slots")
> does. On the other hand, scan_swap_map_slots() needs to reach LATENCY_LIMIT
> before calling cond_resched(), so cond_resched() is needed when failed to
> find available space to avoid softlockup.
Thanks for the patch. The patch itself looks good to me.
I think that it's better to describe the test case in the patch
description directly instead of referring the previous commit.
Best Regards,
Huang, Ying
> Signed-off-by: Longlong Xia <xialonglong1@xxxxxxxxxx>
> ---
> mm/swapfile.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 908a529bca12..4fa440e87cd6 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1100,6 +1100,7 @@ int get_swap_pages(int n_goal, swp_entry_t swp_entries[], int entry_size)
> goto check_out;
> pr_debug("scan_swap_map of si %d failed to find offset\n",
> si->type);
> + cond_resched();
>
> spin_lock(&swap_avail_lock);
> nextsi:
