On 4/2/20 12:57 AM, Pavel Tatashin wrote:
> From: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
>
> deferred_init_memmap() disables interrupts the entire time, so it calls
> touch_nmi_watchdog() periodically to avoid soft lockup splats. Soon it
> will run with interrupts enabled, at which point cond_resched() should
> be used instead.
>
> deferred_grow_zone() makes the same watchdog calls through code shared
> with deferred init but will continue to run with interrupts disabled, so
> it can't call cond_resched().
>
> Pull the watchdog calls up to these two places to allow the first to be
> changed later, independently of the second. The frequency reduces from
> twice per pageblock (init and free) to once per max order block.
>
> Fixes: 3a2d7fa8a3d5 ("mm: disable interrupts while initializing deferred pages")
> Cc: stable@xxxxxxxxxxxxxxx # 4.17+
>
> Signed-off-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
> Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
> ---
> mm/page_alloc.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 3c4eb750a199..e8ff6a176164 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1639,7 +1639,6 @@ static void __init deferred_free_pages(unsigned long pfn,
> } else if (!(pfn & nr_pgmask)) {
> deferred_free_range(pfn - nr_free, nr_free);
> nr_free = 1;
> - touch_nmi_watchdog();
> } else {
> nr_free++;
> }
> @@ -1669,7 +1668,6 @@ static unsigned long __init deferred_init_pages(struct zone *zone,
> continue;
> } else if (!page || !(pfn & nr_pgmask)) {
> page = pfn_to_page(pfn);
> - touch_nmi_watchdog();
> } else {
> page++;
> }
> @@ -1809,8 +1807,10 @@ static int __init deferred_init_memmap(void *data)
> * that we can avoid introducing any issues with the buddy
> * allocator.
> */
> - while (spfn < epfn)
> + while (spfn < epfn) {
> nr_pages += deferred_init_maxorder(&i, zone, &spfn, &epfn);
> + touch_nmi_watchdog();
> + }
> zone_empty:
> pgdat_resize_unlock(pgdat, &flags);
>
> @@ -1894,6 +1894,7 @@ deferred_grow_zone(struct zone *zone, unsigned int order)
> first_deferred_pfn = spfn;
>
> nr_pages += deferred_init_maxorder(&i, zone, &spfn, &epfn);
> + touch_nmi_watchdog();
>
> /* We should only stop along section boundaries */
> if ((first_deferred_pfn ^ spfn) < PAGES_PER_SECTION)
>
