From: Cannon Matthews <cannonmatthews@xxxxxxxxxx> Subject: mm: hugetlb: yield when prepping struct pages When booting with very large numbers of gigantic (i.e. 1G) pages, the operations in the loop of gather_bootmem_prealloc, and specifically prep_compound_gigantic_page, takes a very long time, and can cause a softlockup if enough pages are requested at boot. For example booting with 3844 1G pages requires prepping (set_compound_head, init the count) over 1 billion 4K tail pages, which takes considerable time. Add a cond_resched() to the outer loop in gather_bootmem_prealloc() to prevent this lockup. Tested: Booted with softlockup_panic=1 hugepagesz=1G hugepages=3844 and no softlockup is reported, and the hugepages are reported as successfully setup. Link: http://lkml.kernel.org/r/20180627214447.260804-1-cannonmatthews@xxxxxxxxxx Signed-off-by: Cannon Matthews <cannonmatthews@xxxxxxxxxx> Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Cc: Andres Lagar-Cavilla <andreslc@xxxxxxxxxx> Cc: Peter Feiner <pfeiner@xxxxxxxxxx> Cc: Greg Thelen <gthelen@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/hugetlb.c | 1 + 1 file changed, 1 insertion(+) diff -puN mm/hugetlb.c~mm-hugetlb-yield-when-prepping-struct-pages mm/hugetlb.c --- a/mm/hugetlb.c~mm-hugetlb-yield-when-prepping-struct-pages +++ a/mm/hugetlb.c @@ -2163,6 +2163,7 @@ static void __init gather_bootmem_preall */ if (hstate_is_gigantic(h)) adjust_managed_page_count(page, 1 << h->order); + cond_resched(); } } _
