From 2048e98e9f9d4a8c374248ac520dca679d052896 Mon Sep 17 00:00:00 2001
From: Cannon Matthews <cannonmatthews@google.com>
Date: Tue, 3 Jul 2018 17:02:43 -0700
Subject: [PATCH] mm: hugetlb: yield when prepping struct pages

References: git fixes (memory initialisation)
Patch-mainline: v4.18
Git-commit: 520495fe96d74e05db585fc748351e0504d8f40d

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@google.com
Signed-off-by: Cannon Matthews <cannonmatthews@google.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Peter Feiner <pfeiner@google.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 mm/hugetlb.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 8cda1b4af19f..10f27bdee1a4 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2204,6 +2204,7 @@ static void __init gather_bootmem_prealloc(void)
 		 */
 		if (hstate_is_gigantic(h))
 			adjust_managed_page_count(page, 1 << h->order);
+		cond_resched();
 	}
 }