The patch titled Subject: mm/page_alloc: fix watchdog soft lockups during set_zone_contiguous() has been added to the -mm tree. Its filename is mm-page_alloc-fix-watchdog-soft-lockups-during-set_zone_contiguous.patch

This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/mm-page_alloc-fix-watchdog-soft-loc... and later at http://ozlabs.org/~akpm/mmotm/broken-out/mm-page_alloc-fix-watchdog-soft-loc...

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------------------------------------------------------ From: David Hildenbrand david@redhat.com Subject: mm/page_alloc: fix watchdog soft lockups during set_zone_contiguous()

Without CONFIG_PREEMPT, it can happen that we get soft lockups detected, e.g., while booting up.

[ 105.608900] watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [swapper/0:1] [ 105.608933] Modules linked in: [ 105.608933] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.6.0-next-20200331+ #4 [ 105.608933] Hardware name: Red Hat KVM, BIOS 1.11.1-4.module+el8.1.0+4066+0f1aadab 04/01/2014 [ 105.608933] RIP: 0010:__pageblock_pfn_to_page+0x134/0x1c0 [ 105.608933] Code: 85 c0 74 71 4a 8b 04 d0 48 85 c0 74 68 48 01 c1 74 63 f6 01 04 74 5e 48 c1 e7 06 4c 8b 05 cc 991 [ 105.608933] RSP: 0000:ffffb6d94000fe60 EFLAGS: 00010286 ORIG_RAX: ffffffffffffff13 [ 105.608933] RAX: fffff81953250000 RBX: 000000000a4c9600 RCX: ffff8fe9ff7c1990 [ 105.608933] RDX: ffff8fe9ff7dab80 RSI: 000000000a4c95ff RDI: 0000000293250000 [ 105.608933] RBP: ffff8fe9ff7dab80 R08: fffff816c0000000 R09: 0000000000000008 [ 105.608933] R10: 0000000000000014 R11: 0000000000000014 R12: 0000000000000000 [ 105.608933] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 105.608933] FS: 0000000000000000(0000) GS:ffff8fe1ff400000(0000) knlGS:0000000000000000 [ 105.608933] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 105.608933] CR2: 000000000f613000 CR3: 00000088cf20a000 CR4: 00000000000006f0 [ 105.608933] Call Trace: [ 105.608933] set_zone_contiguous+0x56/0x70 [ 105.608933] page_alloc_init_late+0x166/0x176 [ 105.608933] kernel_init_freeable+0xfa/0x255 [ 105.608933] ? rest_init+0xaa/0xaa [ 105.608933] kernel_init+0xa/0x106 [ 105.608933] ret_from_fork+0x35/0x40

The issue becomes visible when having a lot of memory (e.g., 4TB) assigned to a single NUMA node - a system that can easily be created using QEMU. Inside VMs on a hypervisor with quite some memory overcommit, this is fairly easy to trigger.

Link: http://lkml.kernel.org/r/20200416073417.5003-1-david@redhat.com Signed-off-by: David Hildenbrand david@redhat.com Reviewed-by: Pavel Tatashin pasha.tatashin@soleen.com Reviewed-by: Pankaj Gupta pankaj.gupta.linux@gmail.com Reviewed-by: Baoquan He bhe@redhat.com Reviewed-by: Shile Zhang shile.zhang@linux.alibaba.com Acked-by: Michal Hocko mhocko@suse.com Cc: Kirill Tkhai ktkhai@virtuozzo.com Cc: Shile Zhang shile.zhang@linux.alibaba.com Cc: Pavel Tatashin pasha.tatashin@soleen.com Cc: Daniel Jordan daniel.m.jordan@oracle.com Cc: Michal Hocko mhocko@kernel.org Cc: Alexander Duyck alexander.duyck@gmail.com Cc: Baoquan He bhe@redhat.com Cc: Oscar Salvador osalvador@suse.de Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/page_alloc.c | 1 + 1 file changed, 1 insertion(+)

--- a/mm/page_alloc.c~mm-page_alloc-fix-watchdog-soft-lockups-during-set_zone_contiguous +++ a/mm/page_alloc.c @@ -1607,6 +1607,7 @@ void set_zone_contiguous(struct zone *zo if (!__pageblock_pfn_to_page(block_start_pfn, block_end_pfn, zone)) return; + cond_resched(); }

/* We confirm that there is no hole */ _

Patches currently in -mm which might be from david@redhat.com are

mm-page_alloc-fix-watchdog-soft-lockups-during-set_zone_contiguous.patch drivers-base-memoryc-cache-memory-blocks-in-xarray-to-accelerate-lookup-fix.patch powerpc-pseries-hotplug-memory-stop-checking-is_mem_section_removable.patch mm-memory_hotplug-remove-is_mem_section_removable.patch